Problem when hot, still here!!!
Thread Starter
Melting Slicks
Joined: Nov 2005
Posts: 3,322
Likes: 141
From: Green Valley Arizona
Problem when hot, still here!!!
For the last year I have been fighting a heat releated problem with my
'95....engine begins to cut-out or rev-up and finally dies when the coolant temp stays above 220 or so. I get various DTCs....have replaced the OptiSpark unit twice, coil, ECM twice, ignition module and the problem is still there.
Some have replied that it is still the OptiSpark unit...that it may take several tries to get a new one to work. I have bought both of the ones from the PartsLady which are supposed to be good units..??
I have monitored the engine using my laptop and everything looks fine until the problem begins. This last time DTC 16 was the first one set. Last time it was DTCs for the ignition module.
What to do?
'95....engine begins to cut-out or rev-up and finally dies when the coolant temp stays above 220 or so. I get various DTCs....have replaced the OptiSpark unit twice, coil, ECM twice, ignition module and the problem is still there.
Some have replied that it is still the OptiSpark unit...that it may take several tries to get a new one to work. I have bought both of the ones from the PartsLady which are supposed to be good units..??
I have monitored the engine using my laptop and everything looks fine until the problem begins. This last time DTC 16 was the first one set. Last time it was DTCs for the ignition module.
What to do?
Le Mans Master
Joined: Jan 2006
Posts: 5,620
Likes: 206
From: Orlando FL
Well, you haven’t missed much but you can still never rule anything out with those strange problems.
Two thing come to mind, fuel pressure mainly the pump. Or possibly a bad electrical connection at a connector.
If it only happens when hot is sounds heat related. But is it every time at 220*?
My last thought is ignition switch thought not very good.
Two thing come to mind, fuel pressure mainly the pump. Or possibly a bad electrical connection at a connector.
If it only happens when hot is sounds heat related. But is it every time at 220*?
My last thought is ignition switch thought not very good.
Melting Slicks
Joined: Oct 2004
Posts: 2,510
Likes: 4
From: Austin Texas
I would concentrate on electronic components that are prone to failing at high temperatures:
-ICM (did you remember to put the thermal grease on the new ICM to disapate heat through the heatsink? )
-COIL
I realize that you replaced these already, but you never know......
-ICM (did you remember to put the thermal grease on the new ICM to disapate heat through the heatsink? )
-COIL
I realize that you replaced these already, but you never know......
Last edited by MikeC4; Mar 12, 2009 at 12:17 PM.
Thread Starter
Melting Slicks
Joined: Nov 2005
Posts: 3,322
Likes: 141
From: Green Valley Arizona
Fuel pressure was the first thing I checked when this problem showed-up...solid pressure.
I have wiggled, re-connected connectors, cleaned terminals...etc....trying to find this heat sensitive component.
Oh and yes I used the grease when I replaced the ICM.
The problem occurs everytime after the coolant temp has been in the 220 area for 5 minutes or so. This happens in traffic with little airflow into the radiator. If I turn the AUTO temp on, which turns on the radiator fan(s), I can keep the coolant temp down and all is fine. This worked all winter long, but now that temps are rising here in Tucson, AZ...the coolant temp gets hotter quicker and not able to cool-down as much. Once the problem occurs...even with the fans on it will not recover until after engine dies and cools down for a few minutes.
I am going to swap out the alternator and battery this weekend from my '96, just to see.
I have wiggled, re-connected connectors, cleaned terminals...etc....trying to find this heat sensitive component.
Oh and yes I used the grease when I replaced the ICM.
The problem occurs everytime after the coolant temp has been in the 220 area for 5 minutes or so. This happens in traffic with little airflow into the radiator. If I turn the AUTO temp on, which turns on the radiator fan(s), I can keep the coolant temp down and all is fine. This worked all winter long, but now that temps are rising here in Tucson, AZ...the coolant temp gets hotter quicker and not able to cool-down as much. Once the problem occurs...even with the fans on it will not recover until after engine dies and cools down for a few minutes.
I am going to swap out the alternator and battery this weekend from my '96, just to see.
Safety Car
Joined: Jun 2006
Posts: 3,629
Likes: 28
From: FL
Fuel pressure was the first thing I checked when this problem showed-up...solid pressure.
I have wiggled, re-connected connectors, cleaned terminals...etc....trying to find this heat sensitive component.
Oh and yes I used the grease when I replaced the ICM.
The problem occurs everytime after the coolant temp has been in the 220 area for 5 minutes or so. This happens in traffic with little airflow into the radiator. If I turn the AUTO temp on, which turns on the radiator fan(s), I can keep the coolant temp down and all is fine. This worked all winter long, but now that temps are rising here in Tucson, AZ...the coolant temp gets hotter quicker and not able to cool-down as much. Once the problem occurs...even with the fans on it will not recover until after engine dies and cools down for a few minutes.
I am going to swap out the alternator and battery this weekend from my '96, just to see.
I have wiggled, re-connected connectors, cleaned terminals...etc....trying to find this heat sensitive component.
Oh and yes I used the grease when I replaced the ICM.
The problem occurs everytime after the coolant temp has been in the 220 area for 5 minutes or so. This happens in traffic with little airflow into the radiator. If I turn the AUTO temp on, which turns on the radiator fan(s), I can keep the coolant temp down and all is fine. This worked all winter long, but now that temps are rising here in Tucson, AZ...the coolant temp gets hotter quicker and not able to cool-down as much. Once the problem occurs...even with the fans on it will not recover until after engine dies and cools down for a few minutes.
I am going to swap out the alternator and battery this weekend from my '96, just to see.
Get a shop vac that has a connection that allows it to blow, connect the hose to that port and direct it at various components such as the ICM while it is running bad, the direct high speed air flow will sometimes drop the temperature enough to get it to recover, that may give you clue where to start, good luck.
Melting Slicks
Joined: Oct 2004
Posts: 2,510
Likes: 4
From: Austin Texas
This is just a thought......
My son's '96 LT4 had a situation where his engine bucked and bogged when temp hit about 217*. Hooked up a OBDII code reader, nothing. It took me awhile to figure out what was going on, but when the engine started to act erratic, I noticed that the digital readout from the CTS would quickly jump back and forth between 217* and 222*. I have never seen a CTS jump 5 degrees in the blink of an eye, so I replaced his CTS. Problem solved. The difference of course, is that your engine is shutting down completley, whereas my son's LT4 was sputtering with a faulty CTS....
anyways....just a thought.....
My son's '96 LT4 had a situation where his engine bucked and bogged when temp hit about 217*. Hooked up a OBDII code reader, nothing. It took me awhile to figure out what was going on, but when the engine started to act erratic, I noticed that the digital readout from the CTS would quickly jump back and forth between 217* and 222*. I have never seen a CTS jump 5 degrees in the blink of an eye, so I replaced his CTS. Problem solved. The difference of course, is that your engine is shutting down completley, whereas my son's LT4 was sputtering with a faulty CTS....
anyways....just a thought.....
Thread Starter
Melting Slicks
Joined: Nov 2005
Posts: 3,322
Likes: 141
From: Green Valley Arizona
Since the engine does stay running and does not die, here is something that might be worth a try, it has helped me find similar problems.
Get a shop vac that has a connection that allows it to blow, connect the hose to that port and direct it at various components such as the ICM while it is running bad, the direct high speed air flow will sometimes drop the temperature enough to get it to recover, that may give you clue where to start, good luck.
Get a shop vac that has a connection that allows it to blow, connect the hose to that port and direct it at various components such as the ICM while it is running bad, the direct high speed air flow will sometimes drop the temperature enough to get it to recover, that may give you clue where to start, good luck.
I have thought about getting a can of electronic freeze spray and see if that will locate the component. Guess it is time to try it.
Le Mans Master
Joined: Jan 2006
Posts: 6,564
Likes: 6
From: Woodstock Georgia
I am thinking MikeC4 might be onto something. If the CTS on the front of the water pump is giving erratic readings it can in turn give the ECM/PCM fits trying to compensate for engine temp. Since it also supplies info to the digital gauge the easy check is to watch the digital gauge and see what's happening.
But that doesn't explain the code 16, which is low resolution from the opti spark. Could be the opti or the harness opti to PCM. There is a troubleshooting section in your FSM for verifying the harness is good.
But that doesn't explain the code 16, which is low resolution from the opti spark. Could be the opti or the harness opti to PCM. There is a troubleshooting section in your FSM for verifying the harness is good.
Last edited by aminnich; Mar 12, 2009 at 04:15 PM.
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Safety Car
Joined: Jun 2006
Posts: 3,629
Likes: 28
From: FL
Well....not quite...the engine does die and will not immedately re-start....takes a minute or so and it will re-start for a few seconds...then die. I have to wait a good 20 minutes or so, depending upon air temp at the time before the engine will run smooth and be driveable.
I have thought about getting a can of electronic freeze spray and see if that will locate the component. Guess it is time to try it.
I have thought about getting a can of electronic freeze spray and see if that will locate the component. Guess it is time to try it.
Thread Starter
Melting Slicks
Joined: Nov 2005
Posts: 3,322
Likes: 141
From: Green Valley Arizona
I am thinking MikeC4 might be onto something. If the CTS on the front of the water pump is giving erratic readings it can in turn give the ECM/PCM fits trying to compensate for engine temp. Since it also supplies info to the digital gauge the easy check is to watch the digital gauge and see what's happening.
But that doesn't explain the code 16, which is low resolution from the opti spark. Could be the opti or the harness opti to PCM. There is a troubleshooting section in your FSM for verifying the harness is good.
But that doesn't explain the code 16, which is low resolution from the opti spark. Could be the opti or the harness opti to PCM. There is a troubleshooting section in your FSM for verifying the harness is good.
I have visually inspected the harness...have checked voltages as well. Harness seems to be fine....going to take the one off my '96 when I pull the alternator off this weekend.
When this problem happended just yesterday, I was watching the digital voltage readout. Usually it reads above 14 volts...this time it showed 13.9...dropped to 13.7....and after the engine died, voltage was around 12. Also with the ignition ON, engine not running...I heard several relays clicking away under the hood.....the AIR pump was cycling ON/OFF...all kinds of odd things. This is what has me going to try the alternator.
Thread Starter
Melting Slicks
Joined: Nov 2005
Posts: 3,322
Likes: 141
From: Green Valley Arizona
Yep..I agree...cleaned the battery terminals when the problem first appeared. They had very little on them and it has made no difference.
I did swap-out the alternator this morning, but have not had time to drive it and get the engine hot....hope to tomorrow or Sunday.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Consider cleaning out the front of your radiator (not the evaporator), they catch and hold an amazing amount of leaves, straw, debris which greatly reduces the cooling capacity. There probably is something else going on because even at 222 F, your engine should run ok. When it dies, I would check for spark during cranking and measure the fuel pressure and check for injector pulses with a noid light. Engines need fuel, air, and spark to start and run and clearly you are missing one or more! Guessing and replacing is not the way to fix problems.
Thread Starter
Melting Slicks
Joined: Nov 2005
Posts: 3,322
Likes: 141
From: Green Valley Arizona
Radiator was replaced, twice actually two years ago and the area is clean.
I have checked fuel pressue when the problem is present; its good. I do eed to get a noid light or bring an O'scope home from work again and check futher for pulses. I want to check the low and high resolution pulses from the OptiSpark unit...but I am likely to destroy the harness in getting wires in there to connect to the O'scope.
I agree....more troubleshooting is in order instead of just replacing parts.
I have checked fuel pressue when the problem is present; its good. I do eed to get a noid light or bring an O'scope home from work again and check futher for pulses. I want to check the low and high resolution pulses from the OptiSpark unit...but I am likely to destroy the harness in getting wires in there to connect to the O'scope.
I agree....more troubleshooting is in order instead of just replacing parts.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
When aged, it is common for the spark control module to quit when hot and start working when cooled down. I have seen this a couple of times! SCM's aren't terribly expensive either. For low cost items, I don't see anything wrong in replacing them. See if spark quits when hot.
Safety Car
Joined: Dec 2007
Posts: 3,616
Likes: 5
From: Sandhills of North Carolina
I want to see how this ends because I have the same issue although not quite this extreme. I was told by my mechanic to keep an eye on my alternator. It seems to be working fine but I also get a rough idle/lope after the engine warms up. I also have flickering dash display lights. Voltage can vary just like Lanny's.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
I want to see how this ends because I have the same issue although not quite this extreme. I was told by my mechanic to keep an eye on my alternator. It seems to be working fine but I also get a rough idle/lope after the engine warms up. I also have flickering dash display lights. Voltage can vary just like Lanny's.
Thread Starter
Melting Slicks
Joined: Nov 2005
Posts: 3,322
Likes: 141
From: Green Valley Arizona
The spark control module...is this the same as the ignition control module...it is right?....or do I have it wrong?
I replaced the ignition control module as the DTCs were leading toward it and it was possibly the original....but nope....same problem.
Have not had the car up to temp yet with the alternator from my '96. I also swapped the OptiSpark harness out of the '96 and put into the
'95...just to see. I did not do the battery yet....may do that yet. Will drive the '95 to work tomorrow (Monday) and see what happens???????
I am still going to make a Optispark test harness so I can hook up a O'Scope and take a look at the resolution pulses...and the five volts going into the OptiSpark.
Will update when I know more.
I replaced the ignition control module as the DTCs were leading toward it and it was possibly the original....but nope....same problem.
Have not had the car up to temp yet with the alternator from my '96. I also swapped the OptiSpark harness out of the '96 and put into the
'95...just to see. I did not do the battery yet....may do that yet. Will drive the '95 to work tomorrow (Monday) and see what happens???????
I am still going to make a Optispark test harness so I can hook up a O'Scope and take a look at the resolution pulses...and the five volts going into the OptiSpark.
Will update when I know more.
Race Director
Joined: Apr 2000
Posts: 15,344
Likes: 4,002
From: Texas
Make sure the wires to the starter are tight and corrosion free. I know it seems totally unrelated. I battled a similar issue with mine and that's what it turned out to be. Electrons do funny things.
Thread Starter
Melting Slicks
Joined: Nov 2005
Posts: 3,322
Likes: 141
From: Green Valley Arizona
Results of drive with different alternator and OptiSpark harness:
engine rpm "coughed" a couple of times along with the tach needle bounced....which is how the problem begins. But this time letting engine idle, coolant temp went to 232 and rad fans came on, cooled down to 220 or so and then back up and down again....nothing...no "coughs", no tach needle bounce...nothing.
Drove it again today, will see what happens on trip home this afternoon.
I think "its just messin' with me now".....
engine rpm "coughed" a couple of times along with the tach needle bounced....which is how the problem begins. But this time letting engine idle, coolant temp went to 232 and rad fans came on, cooled down to 220 or so and then back up and down again....nothing...no "coughs", no tach needle bounce...nothing.
Drove it again today, will see what happens on trip home this afternoon.
I think "its just messin' with me now".....