'92 LT1 gets warm...then dies
03-15-2012, 12:35 AM
#1
Team Owner
Pro Mechanic
Thread Starter
'92 LT1 gets warm...then dies
Symptoms started w/a high RPM/WOT miss, a few weeks ago. Figured I'd check fuel pressure when I got time, but hadn't gotten to it when it got worse recently. The RPM at which the misfire started got lower and lower...then it started missing at only part throttle and lower RPM. The missing under those conditions was very violent. It got so bad that I'd want to slip the clutch to avoid drive line (and my neck) shock! While this was going on, the tach would bounce around. I knew then that it was ignition and not fuel related. Finally, it simply died and wouldn't restart...a 1/4 mile from my driveway. After letting it "cool" with the hood open for about 15 minutes, it started, ran incredibly roughly to my house, then stalled and wouldn't restart.
Being an LT1, it MUST be the Opti taking a dump...right?
Being an LT1, it MUST be the Opti taking a dump...right?
03-15-2012, 08:21 AM
#4
Burning Brakes
Sounds like your trouble isnt in a component.
UNLESS....
are you just changing the cap and rotor, or are you replacing the ENTIRE opti? I know it may sound like a dumb question, just have to ask.
If you trouble shoot the opti a bit deeper, then maybe you will find something a little more concrete.
In that trouble shooting guide, it pretty much said if the opti has power and isnt sending out a pulse, its bad. Yet, there is more to it.
I have been through this myself about a year ago, and I racked my brain trying to convince myself it wasnt the opti. I am an electronics tech, and at the time I was in the navy with access to some fancy tools. I took a few home to help me. (dont worry, I returned them
)
This is what I would do in your shoes...
1) Verify Ground on ALL ignition related components.
2) Verify all fuses related to the situation are good.
3) Verify Correct voltage at battery and all components invovled.
these are the first three steps I take in almost any situation. Since you say this happened on a rough road, makes me think something has wiggled loose. I would go as far as checking the connections on the rear of the ECM, unlikely, but hey, its easy to check.
Next is where I would take it a step further.
4) test for spark on #1 (which youve done).
A.) if no spark go to 5.
B.) if spark is present, the icm and coil are working. Trouble lies in timing, high voltage side of opti for other cylinders or else where.
5) Test for spark on coil to opti ignition high voltage wire. First test on the side that connects to the opti. Then test on the coil itself. This is done to ensure the wire itself is good.
A.) if no spark go to 6.
B.) if spark is present, go to X
6) Disconnect the ICM connector. Verify +10v DC or more from PIN A to ground and PIN D to ground on the ICM connector. This tests the coil, and wiring all the way back to the ignition fuse. (key on engine off)
A.) If no voltage, check fuse and wiring.
B.) if correct voltage is present the secondary wiring of the coil could still be bad, but we'll assume its good. Continue to step 7
7) Verify Pulse signal at PIN B of ICM. This is done with a voltmeter or o-scope. It should be a pulse (AC Voltage) that varies between 1-4v. On a scope, it will look like a square wave, Each pulse corresponds to a cylinder firing. (your cranking the engine to get the pulse)
A.) if no pulse, go to 8
B.) if pulse is present, ICM is faulted. Replace, and return to step 4.
8) Verify pulse signal at ECM connector to ICM. PIN B5 (dont have the book infront of me, might want to check that pin location).
a.) if no pulse, go to 9
B.) if pulse is present, the wire or connecton to ICM is faulty. Check continuity, check short to ground. Replace wire, connector, or repair.
9) The signal to the ECM for the ignition comes from the opti. This is where a scope would be handy. Test at both the opti, and the extension cable!!
9.1) Pin A on the opti is Low resolution signal. It will be different for each pulse, but only four variations. So you will see 5 pulses get progessively longer after each other, then reset after 5 pulses. Crank the engine and watch the scope. here is a pic, the low resolution signal comes from the big long slots on the wheel. (the 5th pulse is like a marker for the pcm to know when the cycle restarts, it wont correspond to a cylinder or mechanical event) It will cycle through twice per rotation of the crank.
A) if no signal, optical sensors in the opti are bad. replace opti.
B) if there is signal continue to step 9.2.
9.2) PIN B on the opti is the high resolution, it is the 360 small slots in the optispark trigger wheel. it will pulse 720 times per crankshaft revolution. Use the scope and look for this signal. It may be hard to dial in, but a signal is what you are looking for regardless of how perfect you can get it. You might want to use a scope with the capture feature.
A) if no signal present, the optical sensors arent reading. Replace optispark.
B) if there is signal, go to step 9.3
9.3) PIN C should be 12v (not sure, dont remember). check to ground.
A) if no voltage, check wiring and PCM
B) If voltage is present, go to step 9.4
9.4) Ground. Check continuity on wire.
A) if no ground continuity, inspect wire and PCM
B) if ground is good, Opti is faulty.
After all of this, you have tested the opti, coil, the ICM, the ECM input and output, Voltage on all components and you are left with only one thing that could be wrong...
Cap and Rotor. (btw this is what my problem was, the rotor wasnt secured properly and it came off. I found out AFTER buying the opti.)
Here is some more info:
http://ridingwithposssi.tripod.com/optispark.html
http://www.diyautotune.com/tech_arti...t1_lt4_l99.htm
UNLESS....
are you just changing the cap and rotor, or are you replacing the ENTIRE opti? I know it may sound like a dumb question, just have to ask.
If you trouble shoot the opti a bit deeper, then maybe you will find something a little more concrete.
In that trouble shooting guide, it pretty much said if the opti has power and isnt sending out a pulse, its bad. Yet, there is more to it.
I have been through this myself about a year ago, and I racked my brain trying to convince myself it wasnt the opti. I am an electronics tech, and at the time I was in the navy with access to some fancy tools. I took a few home to help me. (dont worry, I returned them
)This is what I would do in your shoes...
1) Verify Ground on ALL ignition related components.
2) Verify all fuses related to the situation are good.
3) Verify Correct voltage at battery and all components invovled.
these are the first three steps I take in almost any situation. Since you say this happened on a rough road, makes me think something has wiggled loose. I would go as far as checking the connections on the rear of the ECM, unlikely, but hey, its easy to check.
Next is where I would take it a step further.
4) test for spark on #1 (which youve done).
A.) if no spark go to 5.
B.) if spark is present, the icm and coil are working. Trouble lies in timing, high voltage side of opti for other cylinders or else where.
5) Test for spark on coil to opti ignition high voltage wire. First test on the side that connects to the opti. Then test on the coil itself. This is done to ensure the wire itself is good.
A.) if no spark go to 6.
B.) if spark is present, go to X
6) Disconnect the ICM connector. Verify +10v DC or more from PIN A to ground and PIN D to ground on the ICM connector. This tests the coil, and wiring all the way back to the ignition fuse. (key on engine off)
A.) If no voltage, check fuse and wiring.
B.) if correct voltage is present the secondary wiring of the coil could still be bad, but we'll assume its good. Continue to step 7
7) Verify Pulse signal at PIN B of ICM. This is done with a voltmeter or o-scope. It should be a pulse (AC Voltage) that varies between 1-4v. On a scope, it will look like a square wave, Each pulse corresponds to a cylinder firing. (your cranking the engine to get the pulse)
A.) if no pulse, go to 8
B.) if pulse is present, ICM is faulted. Replace, and return to step 4.
8) Verify pulse signal at ECM connector to ICM. PIN B5 (dont have the book infront of me, might want to check that pin location).
a.) if no pulse, go to 9
B.) if pulse is present, the wire or connecton to ICM is faulty. Check continuity, check short to ground. Replace wire, connector, or repair.
9) The signal to the ECM for the ignition comes from the opti. This is where a scope would be handy. Test at both the opti, and the extension cable!!
9.1) Pin A on the opti is Low resolution signal. It will be different for each pulse, but only four variations. So you will see 5 pulses get progessively longer after each other, then reset after 5 pulses. Crank the engine and watch the scope. here is a pic, the low resolution signal comes from the big long slots on the wheel. (the 5th pulse is like a marker for the pcm to know when the cycle restarts, it wont correspond to a cylinder or mechanical event) It will cycle through twice per rotation of the crank.
A) if no signal, optical sensors in the opti are bad. replace opti.
B) if there is signal continue to step 9.2.
9.2) PIN B on the opti is the high resolution, it is the 360 small slots in the optispark trigger wheel. it will pulse 720 times per crankshaft revolution. Use the scope and look for this signal. It may be hard to dial in, but a signal is what you are looking for regardless of how perfect you can get it. You might want to use a scope with the capture feature.
A) if no signal present, the optical sensors arent reading. Replace optispark.
B) if there is signal, go to step 9.3
9.3) PIN C should be 12v (not sure, dont remember). check to ground.
A) if no voltage, check wiring and PCM
B) If voltage is present, go to step 9.4
9.4) Ground. Check continuity on wire.
A) if no ground continuity, inspect wire and PCM
B) if ground is good, Opti is faulty.
After all of this, you have tested the opti, coil, the ICM, the ECM input and output, Voltage on all components and you are left with only one thing that could be wrong...
Cap and Rotor. (btw this is what my problem was, the rotor wasnt secured properly and it came off. I found out AFTER buying the opti.)
Here is some more info:
http://ridingwithposssi.tripod.com/optispark.html
http://www.diyautotune.com/tech_arti...t1_lt4_l99.htm
03-18-2012, 11:03 PM
#5
Team Owner
Pro Mechanic
Thread Starter
I just wrote this for another thread....
5) Test for spark on coil to opti ignition high voltage wire. First test on the side that connects to the opti. Then test on the coil itself. This is done to ensure the wire itself is good.
A.) if no spark go to 6.
B.) if spark is present, go to X
5) Test for spark on coil to opti ignition high voltage wire. First test on the side that connects to the opti. Then test on the coil itself. This is done to ensure the wire itself is good.
A.) if no spark go to 6.
B.) if spark is present, go to X
I originally posted this as a bit of a joke, and the joke has turned and bit me back...a little bit, I think. I posted this b/c I personally don't think the Opti is as bad as many say (and blame). I thought this thread would be loaded with "It's the Opti!"...and I was going to post my (hasty) diagnosis that it was the coil wire.
I installed a spark tester between the coil post and the coil wire, had someone crank and, no spark. I adjusted my spark tester to have a smaller gap (MUCH smaller than necessary at about 1/8") Again, no spark at first...but after several attempts, I finally got a healthy spark; from the tester point to the lower radiator hose! -About 3/4" long. So it has spark. Immediately (and here is the "hasty" part) I determined that it must be the coil wire; There WAS spark, but it (appeared that it) couldn't travel through the wire to get to ground. It "found" ground another way. Si I figured that when it gets hot, the wire must go to infinite resistance. So I bought wires and plugs. When I got the new wires, I ohm'ed the coil wire and it was 680,000 ohms. I checked the old one and to my dismay it ohm'ed the same value. To be sure, I heated the coil wire with a hair drier as hot as I could get it (about 200*) and same reading.
Where I failed was that I didn't check for spark at the end of the coil wire (while the symptom was present) as outlined above.
At this point, I can't see what else it could be other than the cap and rotor. I'll confirm before pulling the water pump, but the optical sensor, ICM, ECM, and coil all work.
Thanks to merlot for the excellent post...now please give me a few minutes to eat my "humble pie".
Last edited by Tom400CFI; 03-18-2012 at 11:06 PM.
03-19-2012, 10:16 AM
#7
ICM's do really stupid things when they fail but if you know you're getting strong spark BEFORE the opti and you're not getting it AFTER the opti, it tells you a few things.
1. Opti pickup, ICM, coil is fine or you would be getting erratic spark before the opti.
2. Almost has to be the cap / rotor.
1. Opti pickup, ICM, coil is fine or you would be getting erratic spark before the opti.
2. Almost has to be the cap / rotor.
03-19-2012, 07:03 PM
#8
Safety Car
ICM's do really stupid things when they fail but if you know you're getting strong spark BEFORE the opti and you're not getting it AFTER the opti, it tells you a few things.
1. Opti pickup, ICM, coil is fine or you would be getting erratic spark before the opti.
2. Almost has to be the cap / rotor.
1. Opti pickup, ICM, coil is fine or you would be getting erratic spark before the opti.
2. Almost has to be the cap / rotor.
03-20-2012, 01:49 PM
#9
Racer
Member Since: Aug 2002
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Symptoms started w/a high RPM/WOT miss, a few weeks ago. Figured I'd check fuel pressure when I got time, but hadn't gotten to it when it got worse recently. The RPM at which the misfire started got lower and lower...then it started missing at only part throttle and lower RPM. The missing under those conditions was very violent. It got so bad that I'd want to slip the clutch to avoid drive line (and my neck) shock! While this was going on, the tach would bounce around. I knew then that it was ignition and not fuel related. Finally, it simply died and wouldn't restart...a 1/4 mile from my driveway. After letting it "cool" with the hood open for about 15 minutes, it started, ran incredibly roughly to my house, then stalled and wouldn't restart.
Being an LT1, it MUST be the Opti taking a dump...right?
Being an LT1, it MUST be the Opti taking a dump...right?
mike
03-25-2012, 10:52 PM
#10
Team Owner
Pro Mechanic
Thread Starter
I am not doing very good here. 
My second mis diagnosis was the "it has spark" but that the spark wasn't making it through the distributor. The reason why that happened, was that the engine was cooling as I was testing, and as it cooled, Spark came back. IDK why it found ground through the lower rad hose, but anyway, upon further testing (and replacing of the plugs and wire since I had bought them, and the origins of the ones on there were unknown), Here is what I now know:
*High RPM is the first to go, as it warms up.
*Tach jumps when the symptom occurs
*Symptom absolutely gets worse as engine temp goes up. When cold...car runs great!
*Not the ICM or coil. I think. I swapped an ICM from my truck ('96 Silverado) and no change. Then I unbolted the ICM/Coil combo from the head, put it in the freezer for a while...then tried again with the Coil/ICM shielded from the heat of the fans/rad with a shop towel. Same results and when the engine shut down on this one, the coil/ICM was maybe 100*F. Not hot.
*Basically, as soon as the fans come on, the symptom starts shortly thereafter. (The symptoms that occur at idle) In less than 5 minutes the car won't run. At that point, there is NO SPARK.
*When it cools, spark comes back and I can fire it back up.
*With my spark tester hooked up, I can't perceive any missed sparks, when the symptom starts, but right before the car stalls (and when it's running REALLY poorly), the spark starts getting erratic, then throwing some WEIRD arcs; big, bright curved ones, not even sounding, I should take a vid of it. Then, as the car dies, there are still intermittent sparks being thrown, but the engine acts like you shut the key off.
*The diagnostic process above didn't work for me. Pins seam to be mislabelled and that makes it tough. For some reason, Mitchell online isn't working from home, so I'll have to look at it at work and print some pages out when I get back to work.
Right now...I think the optical sensor is getting hot and taking a dump.
My second mis diagnosis was the "it has spark" but that the spark wasn't making it through the distributor. The reason why that happened, was that the engine was cooling as I was testing, and as it cooled, Spark came back. IDK why it found ground through the lower rad hose, but anyway, upon further testing (and replacing of the plugs and wire since I had bought them, and the origins of the ones on there were unknown), Here is what I now know:
*High RPM is the first to go, as it warms up.
*Tach jumps when the symptom occurs
*Symptom absolutely gets worse as engine temp goes up. When cold...car runs great!
*Not the ICM or coil. I think. I swapped an ICM from my truck ('96 Silverado) and no change. Then I unbolted the ICM/Coil combo from the head, put it in the freezer for a while...then tried again with the Coil/ICM shielded from the heat of the fans/rad with a shop towel. Same results and when the engine shut down on this one, the coil/ICM was maybe 100*F. Not hot.
*Basically, as soon as the fans come on, the symptom starts shortly thereafter. (The symptoms that occur at idle) In less than 5 minutes the car won't run. At that point, there is NO SPARK.
*When it cools, spark comes back and I can fire it back up.
*With my spark tester hooked up, I can't perceive any missed sparks, when the symptom starts, but right before the car stalls (and when it's running REALLY poorly), the spark starts getting erratic, then throwing some WEIRD arcs; big, bright curved ones, not even sounding, I should take a vid of it. Then, as the car dies, there are still intermittent sparks being thrown, but the engine acts like you shut the key off.
*The diagnostic process above didn't work for me. Pins seam to be mislabelled and that makes it tough. For some reason, Mitchell online isn't working from home, so I'll have to look at it at work and print some pages out when I get back to work.
Right now...I think the optical sensor is getting hot and taking a dump.
Last edited by Tom400CFI; 03-25-2012 at 11:00 PM.
03-26-2012, 09:57 AM
#11
Burning Brakes
Tom,
As a former elctro-optical technician from the military, I can tell you heat produced by the engine will not effect these optical sensors. There just isnt any heat sensitivity in those components, unless they were already damaged physically... but then you wouldnt beable to run at all. The optical sensors are nothing more than a pair of LED's, one sends and one recieves, its low voltage low current. Since they are diodes, they dont fail progressively, they fail all at once. The supporting circuits inside are likely no more than a resistor, which could fail under heat, and get progessively worse, but in this event, it is likely they will fail open, causing no input to the ecm from either optical sensor. There might also be a small transistor inside, like pictured, which could fail under heat, but I think it would take a bunch for these to fail, unless they were cheap components. this is a little pic of how it works inside.
Having said that, I am still curious of what could be causing the problems when warm.
Lets see if I can talk my way through it....
When the engine is running and its in open loop, it runs fine. As soon as it warms up enough to kick on the fans, closed loop, it faults, stumbles and dies.
So what happens when it is in closed loop, that is not happening in open loop?
When a car is started, the computer is in open loop until certain criteria is met. When the sensors are heated up, the car goes into closed loop and the O2 sensors make their corrections.
The PCM will go back into open loop under a variety of conditions. Throttle Position (TP) is one way.There are parameters in the computer that determine what the TP is for Open Loop, and other things. When that TP is reached, and the car goes open loop, and richens up
In open loop, the fueling is purely based off the MAF transfer function and the open loop fuel table. This table has to be calibrated any time you make MAF changes, and changes that affect the airflow of the MAF.
When a car is started, the computer is in open loop until certain criteria is met. The o2 sensors and the coolant need to be heated to work properly, so this is the main reason there is a delay.
Soooo....
We know your car is going into closed loop, so the coolant temp sensor is working, and the o2 sensors are switching, and the PCM is recognizing the time delay. The problem is AFTER you are in closed loop.
I wonder...
Is the ICM working when hot?
Are your o2 sensors up to snuff?
Is the opti working when the failure happens?
Is your fuel pressure correct when the car dies?
Is your MAF sensor good to go?
Is your MAP sensor up to par?
Beyond this, if the opti is testing fine, the rest of the ignition tests good, o2's are good, MAF and MAP, and fuel pressure is good... we get into crazy once in a lifetime errors. Ive read about things from a grounded oil level sensor, to bad grounds on the back of the head. All with similar reports of "car dies when warm, tach freaks out"
Some have reported that the opti-spark its self was bad, and after replacing it, things were great.
I also have read much about replacting the o2 sensors with AC Delco's and the problem was fixed.
While others had a failing coolant temp sensor (with code) and its replacement solved the problem.
Basically, were going to need more hard data to get you somewhere.
When the engine dies, immediatly test the ICM... this will rule it out with the heat issues.
If the ICM is working (signal coming out when cranking) then the opti is working and the ICM is working.
IF NOT, go to the opti. If the opti is not producing signal when cranking, and has power (during/after the failure) then the opti is likely the culprit.
If the opti is producing signal, the icm is producing signal, and the coil is producing spark, then the high voltage side of the opti could be the culprit, but this should be an "all the time" failure.
Now if the ICM is working, opti is working, and ther are sparks on all plug wires... then we have another problem going on.
At this point I would start low and work my way high. First datalog the PCM. This will give the tell tale signs of the failure.
Make sure the o2's are switching, and are reading. If not, replace and re-test.
Make sure the reading from the coolant temp sensor is moving in accordance with the temp
Then make sure the reading from the MAF is correct.
Then make sure the MAP is reading correctly.
Then I would double check my grounds, making absolutely sure every one of them is perfectly clean.
From there, I would start looking for stuff I might have missed.
At this point, I would start looking at stuff that could only happen in the twilight zone.
I hope this helps some.
As a former elctro-optical technician from the military, I can tell you heat produced by the engine will not effect these optical sensors. There just isnt any heat sensitivity in those components, unless they were already damaged physically... but then you wouldnt beable to run at all. The optical sensors are nothing more than a pair of LED's, one sends and one recieves, its low voltage low current. Since they are diodes, they dont fail progressively, they fail all at once. The supporting circuits inside are likely no more than a resistor, which could fail under heat, and get progessively worse, but in this event, it is likely they will fail open, causing no input to the ecm from either optical sensor. There might also be a small transistor inside, like pictured, which could fail under heat, but I think it would take a bunch for these to fail, unless they were cheap components. this is a little pic of how it works inside.
Having said that, I am still curious of what could be causing the problems when warm.
Lets see if I can talk my way through it....
When the engine is running and its in open loop, it runs fine. As soon as it warms up enough to kick on the fans, closed loop, it faults, stumbles and dies.
So what happens when it is in closed loop, that is not happening in open loop?
When a car is started, the computer is in open loop until certain criteria is met. When the sensors are heated up, the car goes into closed loop and the O2 sensors make their corrections.
The PCM will go back into open loop under a variety of conditions. Throttle Position (TP) is one way.There are parameters in the computer that determine what the TP is for Open Loop, and other things. When that TP is reached, and the car goes open loop, and richens up
In open loop, the fueling is purely based off the MAF transfer function and the open loop fuel table. This table has to be calibrated any time you make MAF changes, and changes that affect the airflow of the MAF.
When a car is started, the computer is in open loop until certain criteria is met. The o2 sensors and the coolant need to be heated to work properly, so this is the main reason there is a delay.
Soooo....
We know your car is going into closed loop, so the coolant temp sensor is working, and the o2 sensors are switching, and the PCM is recognizing the time delay. The problem is AFTER you are in closed loop.
I wonder...
Is the ICM working when hot?
Are your o2 sensors up to snuff?
Is the opti working when the failure happens?
Is your fuel pressure correct when the car dies?
Is your MAF sensor good to go?
Is your MAP sensor up to par?
Beyond this, if the opti is testing fine, the rest of the ignition tests good, o2's are good, MAF and MAP, and fuel pressure is good... we get into crazy once in a lifetime errors. Ive read about things from a grounded oil level sensor, to bad grounds on the back of the head. All with similar reports of "car dies when warm, tach freaks out"
Some have reported that the opti-spark its self was bad, and after replacing it, things were great.
I also have read much about replacting the o2 sensors with AC Delco's and the problem was fixed.
While others had a failing coolant temp sensor (with code) and its replacement solved the problem.
Basically, were going to need more hard data to get you somewhere.
When the engine dies, immediatly test the ICM... this will rule it out with the heat issues.
If the ICM is working (signal coming out when cranking) then the opti is working and the ICM is working.
IF NOT, go to the opti. If the opti is not producing signal when cranking, and has power (during/after the failure) then the opti is likely the culprit.
If the opti is producing signal, the icm is producing signal, and the coil is producing spark, then the high voltage side of the opti could be the culprit, but this should be an "all the time" failure.
Now if the ICM is working, opti is working, and ther are sparks on all plug wires... then we have another problem going on.
At this point I would start low and work my way high. First datalog the PCM. This will give the tell tale signs of the failure.
Make sure the o2's are switching, and are reading. If not, replace and re-test.
Make sure the reading from the coolant temp sensor is moving in accordance with the temp
Then make sure the reading from the MAF is correct.
Then make sure the MAP is reading correctly.
Then I would double check my grounds, making absolutely sure every one of them is perfectly clean.
From there, I would start looking for stuff I might have missed.
At this point, I would start looking at stuff that could only happen in the twilight zone.
I hope this helps some.
Last edited by merlot566jka; 03-26-2012 at 09:59 AM.
03-26-2012, 07:31 PM
#12
Safety Car
To add to this and to your theory of the optical signals dropping out.
IF you can datalog or have access to a scan tool w/live engine data watch the High Resolution signal and low res. signal as the engine runs and then dies. Then crank it and see if you have those two signals and they have good counting on the high side and the correct low side millisecond readings. If those are present and correct the Opti-part is ok. the Spark part is the second part of the equation.
I had something similar this past winter the car would misfire at idle when hot and only hot. Then not want to start. Cools down and will start. I was lossing spark going to the Cap, via a inline spark checker. However, once it would misfire I would shut if off, crank and have spark, but the car would try to start but could not until it cooled down. I got a ICM and ironically since I put the car on the road it has been perfect. So I'm going to wait and see... I carry the ICM just in case. I also checked and adjusted pin fit for the opti-spark harness on mine. I'm going to be interested to see what you find out.
I still suspect something funky with your cap and rotor and I suspect this on my car as well. But until it fails...I'm leaving it alone I got AAA.
Last edited by 93Rubie; 03-26-2012 at 07:38 PM.
03-26-2012, 10:12 PM
#13
I had a similar problem, car starts fine cold, runs 20 min, until fully warm then dies. Won't restart until fully cooled down. It was the connector to the ICM. When it was cold it would make contact with the pins inside, when warm they moved just enough so there was no spark. I started the motor and began jiggling all the connectors under the hood, when I jiggled the connector to the ICM the motor stumbled, when I moved it again it died. I opened the connector and bent each pin slightly, problem solved. Worth a try, good luck.
03-26-2012, 11:13 PM
#14
Team Owner
Pro Mechanic
Thread Starter
Whoo-boy! These are some FANTASTIC posts! Thanks to you guys for putting in the time to think about this, and type everything out. I'll answer piece by piece...
Got it. Thanks for the explanation.
It helps. I will report back, what I find. My scan tool is an old OTC and I'm not sure if I can witness the activities of the opti but will try and report back.
Yep. I thought of that too...just for the age of the car. I've shaken, plugged and unplugged, checked connectors. I think the connections are O.K....but I'll check that again. Incredible the similarities between our issues!
So what happens when it is in closed loop, that is not happening in open loop? The problem is AFTER you are in closed loop.
I wonder...
Is the ICM working when hot? I THINK so; 1) because during one test, I swapped in the ICM from my truck...problem remained the same. 2) because during another test, I "froze" the ICM/coil before the test, and when the car stalled out (hot) the ICM was no more than 100*F
Are your o2 sensors up to snuff? I don't know
Is the opti working when the failure happens? I don't know
Is your fuel pressure correct when the car dies? YES. I have checked this twice. First b/c of the original symptom of high load/RPM break up, and second because during testing, I noticed that when the symptom showed up, I could go WOT in neutral and it wouldn't go above 3500 RPM..and it would backfire through the intake -a sign of a lean mixture. Fuel pressure has remained consistent at 40 PSIG idle and 45 PSIG WOT...every time.
Is your MAF sensor good to go? No MAF. Speed/Density car.
Is your MAP sensor up to par? I don't know.
When the engine dies, immediatly test the ICM... this will rule it out with the heat issues. Been trying to, but it's hard; I only have about 10 minutes to test; it only takes about 10 minutes w/the hood open to cool enough to start working again. Then I can't test until I run it and get it up against the fans again.
If the ICM is working (signal coming out when cranking) then the opti is working and the ICM is working.
IF NOT, go to the opti. If the opti is not producing signal when cranking, and has power (during/after the failure) then the opti is likely the culprit.
If the opti is producing signal, the icm is producing signal, and the coil is producing spark, then the high voltage side of the opti could be the culprit, but this should be an "all the time" failure.
Now if the ICM is working, opti is working, and ther are sparks on all plug wires... then we have another problem going on.
At this point I would start low and work my way high. First datalog the PCM. This will give the tell tale signs of the failure. I hope this helps some.
I wonder...
Is the ICM working when hot? I THINK so; 1) because during one test, I swapped in the ICM from my truck...problem remained the same. 2) because during another test, I "froze" the ICM/coil before the test, and when the car stalled out (hot) the ICM was no more than 100*F
Are your o2 sensors up to snuff? I don't know
Is the opti working when the failure happens? I don't know
Is your fuel pressure correct when the car dies? YES. I have checked this twice. First b/c of the original symptom of high load/RPM break up, and second because during testing, I noticed that when the symptom showed up, I could go WOT in neutral and it wouldn't go above 3500 RPM..and it would backfire through the intake -a sign of a lean mixture. Fuel pressure has remained consistent at 40 PSIG idle and 45 PSIG WOT...every time.
Is your MAF sensor good to go? No MAF. Speed/Density car.
Is your MAP sensor up to par? I don't know.
When the engine dies, immediatly test the ICM... this will rule it out with the heat issues. Been trying to, but it's hard; I only have about 10 minutes to test; it only takes about 10 minutes w/the hood open to cool enough to start working again. Then I can't test until I run it and get it up against the fans again.
If the ICM is working (signal coming out when cranking) then the opti is working and the ICM is working.
IF NOT, go to the opti. If the opti is not producing signal when cranking, and has power (during/after the failure) then the opti is likely the culprit.
If the opti is producing signal, the icm is producing signal, and the coil is producing spark, then the high voltage side of the opti could be the culprit, but this should be an "all the time" failure.
Now if the ICM is working, opti is working, and ther are sparks on all plug wires... then we have another problem going on.
At this point I would start low and work my way high. First datalog the PCM. This will give the tell tale signs of the failure. I hope this helps some.
I had a similar problem, car starts fine cold, runs 20 min, until fully warm then dies. Won't restart until fully cooled down. It was the connector to the ICM. When it was cold it would make contact with the pins inside, when warm they moved just enough so there was no spark. I started the motor and began jiggling all the connectors under the hood, when I jiggled the connector to the ICM the motor stumbled, when I moved it again it died. I opened the connector and bent each pin slightly, problem solved. Worth a try, good luck.
Last edited by Tom400CFI; 03-26-2012 at 11:20 PM.
03-27-2012, 11:06 AM
#15
Burning Brakes
Whoo-boy! These are some FANTASTIC posts! Thanks to you guys for putting in the time to think about this, and type everything out. I'll answer piece by piece...
Got it. Thanks for the explanation.
Is the ICM working when hot? I THINK so; 1) because during one test, I swapped in the ICM from my truck...problem remained the same. 2) because during another test, I "froze" the ICM/coil before the test, and when the car stalled out (hot) the ICM was no more than 100*F
if you swapped with your truck, and it still repeated the failure (as long as the ICM's were the same) then we can rule out the icm.... but not the connector
When the engine dies, immediatly test the ICM... this will rule it out with the heat issues. Been trying to, but it's hard; I only have about 10 minutes to test; it only takes about 10 minutes w/the hood open to cool enough to start working again. Then I can't test until I run it and get it up against the fans again.
try these! Splice into each of the 4 wires, run the 4 splice wires back to the cab or where ever, then as soon as it happens, break out the dvm and test it without even opening the hood.
It helps. I will report back, what I find. My scan tool is an old OTC and I'm not sure if I can witness the activities of the opti but will try and report back.
Yep. I thought of that too...just for the age of the car. I've shaken, plugged and unplugged, checked connectors. I think the connections are O.K....but I'll check that again. Incredible the similarities between our issues!
Got it. Thanks for the explanation.
Is the ICM working when hot? I THINK so; 1) because during one test, I swapped in the ICM from my truck...problem remained the same. 2) because during another test, I "froze" the ICM/coil before the test, and when the car stalled out (hot) the ICM was no more than 100*F
if you swapped with your truck, and it still repeated the failure (as long as the ICM's were the same) then we can rule out the icm.... but not the connector
When the engine dies, immediatly test the ICM... this will rule it out with the heat issues. Been trying to, but it's hard; I only have about 10 minutes to test; it only takes about 10 minutes w/the hood open to cool enough to start working again. Then I can't test until I run it and get it up against the fans again.
try these! Splice into each of the 4 wires, run the 4 splice wires back to the cab or where ever, then as soon as it happens, break out the dvm and test it without even opening the hood.
It helps. I will report back, what I find. My scan tool is an old OTC and I'm not sure if I can witness the activities of the opti but will try and report back.
Yep. I thought of that too...just for the age of the car. I've shaken, plugged and unplugged, checked connectors. I think the connections are O.K....but I'll check that again. Incredible the similarities between our issues!
04-03-2012, 12:06 AM
#16
Team Owner
Pro Mechanic
Thread Starter
Update:
I haven't had much time to address this and today was the first time I've touched the thing since my last post. I printed out the diagnostic procedure from Mitchell and it said something painfully obvious that I hadn't thought of:
With the scan tool hooked up, scan engine RPM during cranking. Geeze. Why didn't I think of that?? Grrr.
So today was FULL of surprises.
Surprise #1. When I hooked up the scan tool, I had three codes stored. A surprise, b/c I don't recall EVER seeing a SES illuminate. Codes 16, 36, 42. Makes sense.
Cleared codes and warmed the car up. Problem didn't surface after three fan cycles today, and I believe that is because the ambient temp is much lower; it snowed all day today, and last time I fiddled with it, it was ~65*F. Anyway, after three fan cycles, I closed the hood to trap in heat, and after one more fan cycle, the symptom hit. Within 3 minutes the car was dead. No RPM shown on the scan tool, while cranking. At the same time, it threw a code 16.
Surprise #2. Other scanned observations:
A. MAT started (cold -ambient temp about 35*F) reading 207* and dropped down to ~170* when the car was FULLY hot, hood closed. I think I need a new MAT sensor...lol.
B. TCC indicator light on the scan tool would illuminate quickly, once every 3-4 minutes or so. Car is a 6 speed, so that's weird.
C. At the same time the TCC indicator would flash, the Run Timer would go from whatever the run time was, to 99.9...then right back to the real run time; 28.1min for example.
D. WHILE the symptom was occurring, for that 2-3 min while its running really rough, but w/a little throttle, I can keep it going, my scan tool showed these codes: 13, 14, 16, 22, 23, 25, 26, 27, 33, 34, 35, 36, and 42. Then...FINALLY, I saw an SES light come on, and the scan tool showed codes 13, 14, 16, 36, 42, 61, 62, 63. Then it died. Yikes. I made the mistake of turning the key off, and when I turned it back on and checked codes, I only had these stored: 13, 14, 16, 22, 23, 36, and 42. "Only". :/
Surprise #3. That all these codes show up...and that most of them only show when the symptom occurs. Not before (when its running, but still cold).
Surprise #4. Car wouldn't go into closed loop (or didn't show it was in Closed loop on the scan tool). Long after it was FULLY warmed up (and had gone through two fan cycles), it was still showing open loop. Only after I touched the throttle for the first time, did it then show a jump into closed loop where it stayed.
That's about it for "surprises". Now for some other observations and questions.
1. While the car was running O.K. and idling, the Low res data stream on my scan tool showed generally, ~22. WTF does "22" mean? 22 readings/second?
2. When the symptom showed up, Low res signal dropped to "000" but intermittently jumped to 15, 14...something in that range. Mostly "000" though, which makes sense given that I'm losing spark at that same time.
3. The High Res data stream on my scan tool basically starts at "0" and goes up to 255, then starts a "0" again and counts up again. What is that? Does a '92 ECM still only have the ability to count to 255?? More importantly, what am I looking for here? It took about 20 seconds for it to count from 0-255 when it was running right. When the symptom occurred, I didn't notice what was going on there b/c there were too many other things I was looking at/writing down.
4. When the tach starts jumping all over, the "tach" on the scan tool's data stream is also all over the place. No surprise there, I guess.
According to my tech data, then next step when there is no RPM while cranking is to test for power, KOEO at the yellow wire at distributor harness/plug. I was out of time after the test and had to do dinner/kid to bed, so another time to test that. For now, I'm inclined to ignore that barrage of codes and keep chasing the ignition issue, since they only showed up when everything was going to chit. So I sort of have a plan to pursue, but if anyone has thoughts...share away!
I haven't had much time to address this and today was the first time I've touched the thing since my last post. I printed out the diagnostic procedure from Mitchell and it said something painfully obvious that I hadn't thought of:
With the scan tool hooked up, scan engine RPM during cranking. Geeze. Why didn't I think of that?? Grrr.
So today was FULL of surprises.
Surprise #1. When I hooked up the scan tool, I had three codes stored. A surprise, b/c I don't recall EVER seeing a SES illuminate. Codes 16, 36, 42. Makes sense.
Cleared codes and warmed the car up. Problem didn't surface after three fan cycles today, and I believe that is because the ambient temp is much lower; it snowed all day today, and last time I fiddled with it, it was ~65*F. Anyway, after three fan cycles, I closed the hood to trap in heat, and after one more fan cycle, the symptom hit. Within 3 minutes the car was dead. No RPM shown on the scan tool, while cranking. At the same time, it threw a code 16.
Surprise #2. Other scanned observations:
A. MAT started (cold -ambient temp about 35*F) reading 207* and dropped down to ~170* when the car was FULLY hot, hood closed. I think I need a new MAT sensor...lol.
B. TCC indicator light on the scan tool would illuminate quickly, once every 3-4 minutes or so. Car is a 6 speed, so that's weird.
C. At the same time the TCC indicator would flash, the Run Timer would go from whatever the run time was, to 99.9...then right back to the real run time; 28.1min for example.
D. WHILE the symptom was occurring, for that 2-3 min while its running really rough, but w/a little throttle, I can keep it going, my scan tool showed these codes: 13, 14, 16, 22, 23, 25, 26, 27, 33, 34, 35, 36, and 42. Then...FINALLY, I saw an SES light come on, and the scan tool showed codes 13, 14, 16, 36, 42, 61, 62, 63. Then it died. Yikes. I made the mistake of turning the key off, and when I turned it back on and checked codes, I only had these stored: 13, 14, 16, 22, 23, 36, and 42. "Only". :/
Surprise #3. That all these codes show up...and that most of them only show when the symptom occurs. Not before (when its running, but still cold).
Surprise #4. Car wouldn't go into closed loop (or didn't show it was in Closed loop on the scan tool). Long after it was FULLY warmed up (and had gone through two fan cycles), it was still showing open loop. Only after I touched the throttle for the first time, did it then show a jump into closed loop where it stayed.
That's about it for "surprises". Now for some other observations and questions.
1. While the car was running O.K. and idling, the Low res data stream on my scan tool showed generally, ~22. WTF does "22" mean? 22 readings/second?
2. When the symptom showed up, Low res signal dropped to "000" but intermittently jumped to 15, 14...something in that range. Mostly "000" though, which makes sense given that I'm losing spark at that same time.
3. The High Res data stream on my scan tool basically starts at "0" and goes up to 255, then starts a "0" again and counts up again. What is that? Does a '92 ECM still only have the ability to count to 255?? More importantly, what am I looking for here? It took about 20 seconds for it to count from 0-255 when it was running right. When the symptom occurred, I didn't notice what was going on there b/c there were too many other things I was looking at/writing down.
4. When the tach starts jumping all over, the "tach" on the scan tool's data stream is also all over the place. No surprise there, I guess.
According to my tech data, then next step when there is no RPM while cranking is to test for power, KOEO at the yellow wire at distributor harness/plug. I was out of time after the test and had to do dinner/kid to bed, so another time to test that. For now, I'm inclined to ignore that barrage of codes and keep chasing the ignition issue, since they only showed up when everything was going to chit. So I sort of have a plan to pursue, but if anyone has thoughts...share away!
Last edited by Tom400CFI; 04-03-2012 at 12:22 AM.
04-03-2012, 01:42 AM
#17
3rd Gear
Member Since: Apr 2012
Location: Midwest
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Envy your ability to so thoroughly work through your troubleshooting. I'm not as nearly technically experienced, but going through a *somewhat* similar problem with my '94 missing once it's been driven for a while and gets over about 200* in stop and go city driving. Almost like clockwork, as soon as I pass that center line, it begins to miss badly at idle. Once I begin cruising down the road, it's fine, except for a little bogging off the line. I also believe it is the Opti, but I'm watching your thread closely to see what you find.
04-03-2012, 08:37 PM
#18
Safety Car
Tom, very good work. Not having RPM and low res. and high res. to me says Opti problem. This as long as the electrical to and from the unit is ok during this time it is acting up. I recommended you check and tighten all pin fits to the Opti spark connectors.
Its possible to have a bad connection/harness issue as well.
To answer some of your questions:
The 22 Low res. signal means there is 22m/sec between slits that the low res. sensor picks up.
The high res. signal does count up like you observed and to about what you said.
Sounds like your losing low res. and high res. signals when the unit gets hot. If you lose this ECM cannot run ICM, ICM cannot fire coil=No spark.
Not sure on the intermittent data, but from my experience these older OBDI cars tend to do that. Not sure why. Same with the open/closed loop thing I have observed this happen in my 93, with my scan tool hooked up.
I would pursue like you said, the ignition issue and ignore the other stuff. Fix what you KNOW is bad first.
Its possible to have a bad connection/harness issue as well.
To answer some of your questions:
The 22 Low res. signal means there is 22m/sec between slits that the low res. sensor picks up.
The high res. signal does count up like you observed and to about what you said.
Sounds like your losing low res. and high res. signals when the unit gets hot. If you lose this ECM cannot run ICM, ICM cannot fire coil=No spark.
Not sure on the intermittent data, but from my experience these older OBDI cars tend to do that. Not sure why. Same with the open/closed loop thing I have observed this happen in my 93, with my scan tool hooked up.
I would pursue like you said, the ignition issue and ignore the other stuff. Fix what you KNOW is bad first.
04-09-2012, 04:15 PM
#19
Team Owner
Pro Mechanic
Thread Starter
FINALLY, an update. First day off again, since the last time that I posted. :/
You are correct. As the engine gets warm and the symptom begines to show, I lose low res (first noticeable on the scan tool), then it throws a high res code, the an EST Grounded (code 42)... then dies. Today, I started with a cold engine, and pointed a hair drier on high (about 210*F) directly at the distributor. I let that run for about an hour until the face of the dist was too hot to touch. Car fired right up instantly, and ran perfectly. Once the oil temp got up to 100, I matted it and it revved to 5500 seamlessly -not a single discernible miss. So as merlot said, the Opti doesn't appear to be affected by the heat. At least not by using the "hair drier test". I have to admit; the "hair drier test" is not found in any technical diagnostic manuals. Lol.
Having completed that test, and having a dead car sitting there, I proceeded with the Mitchell diagnostic process. Here it is:
1. Scan the VATS enable with a scan tool. If enable does not.... Blah blah... It starts when cold so it's not VATS.
2. Scan engine RPM during cranking. If RPM is indicated on the scan tool, then go to step 4). If RPM is not indicated on testerNo RPM shown on Scan tool., turn ignition off. Disconnect distributor electrical connector. Turn ignition on. Probe Yellow wire of distributor harness connector (ECM side)with a test light connected to ground. IF light is on, go to next step. Light illuminated
3. Turn ignition off. Check for continuity between ground and distributor harness connector terminal "D" (Black/pink wire). If continuity exists continuity was good. Even did the "pull/shake test" while checking and found no breach of continuity here, problem is faulty distributor connector connection, or faulty distributor.
No need to go on with the procedure here, b/c flowing this process, I'm at the end.
There is no guarantee that I got the entire dist. assy up to full temp w/the hair drier. It was a test, but it didn't necessarily "prove" anything. It was evidence, but not proof. I'm going to try one more thing when it cools and I'll report back in a bit...
-Tom
Having completed that test, and having a dead car sitting there, I proceeded with the Mitchell diagnostic process. Here it is:
1. Scan the VATS enable with a scan tool. If enable does not.... Blah blah... It starts when cold so it's not VATS.
2. Scan engine RPM during cranking. If RPM is indicated on the scan tool, then go to step 4). If RPM is not indicated on testerNo RPM shown on Scan tool., turn ignition off. Disconnect distributor electrical connector. Turn ignition on. Probe Yellow wire of distributor harness connector (ECM side)with a test light connected to ground. IF light is on, go to next step. Light illuminated
3. Turn ignition off. Check for continuity between ground and distributor harness connector terminal "D" (Black/pink wire). If continuity exists continuity was good. Even did the "pull/shake test" while checking and found no breach of continuity here, problem is faulty distributor connector connection, or faulty distributor.
No need to go on with the procedure here, b/c flowing this process, I'm at the end.
There is no guarantee that I got the entire dist. assy up to full temp w/the hair drier. It was a test, but it didn't necessarily "prove" anything. It was evidence, but not proof. I'm going to try one more thing when it cools and I'll report back in a bit...
-Tom
Last edited by Tom400CFI; 04-09-2012 at 04:23 PM.
04-09-2012, 07:04 PM
#20
Safety Car
Something I would try first before a new distributor. Check the pin fit at the connector at the Opti and the one at the ICM. Also check the connector near the vacuum ports on the pass. side of the intake manifold for the Opti. I use a very small eyeglass screw driver and carefully adjust them tighter. I did this to my 93 recently.
IF that fails, Opti-Spark time. Call Petris Enterprises, they seem to have a good reputation and what appears to be a quality replacement kit with vacuum harness and all. If mine fails, that is who I'll probably get one from.
The hair dryer is a good idea. I doubt it got the entire thing hot however. I think the best way is to let it run.
IF that fails, Opti-Spark time. Call Petris Enterprises, they seem to have a good reputation and what appears to be a quality replacement kit with vacuum harness and all. If mine fails, that is who I'll probably get one from.
The hair dryer is a good idea. I doubt it got the entire thing hot however. I think the best way is to let it run.
