1992 Misfire
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From: Chardon Ohio
1992 Misfire
Misfire developed about a week ago. Seemed to only happen at low RPM but not 100% sure since it has 1.6RR and full custom exhaust so it's hard to tell.
Things replaced BEFORE misfire:
Autolite Plugs gapped to .050
Bosch Wires
Fuel pressure reg
Water pump
Underdrive crank pulley
Pcmforless tune
1.6RR
AIR delete
EGR delete (tuned out also)
Long tube headers and full exhaust
PCV valve
Things installed AFTER misfire began to attempt to fix:
NGK Coppers gapped to .050
Both O2 sensors
Seafoamed through vacuum and fuel
Reset the lash on 1.6RR
Reset computer
Cleaned throttle body
MSD ignition coil
Really stumped here guys.. car runs and feels great but at an idle it randomly misfires.. no sequence or pattern. No sputtering or backfires(other than what normally associates with aftermarket exhaust). Not sure if this COULD be Opti or not.. just wanted to get some advice before I throw another $230 at it.
Thanks,
Jon
Things replaced BEFORE misfire:
Autolite Plugs gapped to .050
Bosch Wires
Fuel pressure reg
Water pump
Underdrive crank pulley
Pcmforless tune
1.6RR
AIR delete
EGR delete (tuned out also)
Long tube headers and full exhaust
PCV valve
Things installed AFTER misfire began to attempt to fix:
NGK Coppers gapped to .050
Both O2 sensors
Seafoamed through vacuum and fuel
Reset the lash on 1.6RR
Reset computer
Cleaned throttle body
MSD ignition coil
Really stumped here guys.. car runs and feels great but at an idle it randomly misfires.. no sequence or pattern. No sputtering or backfires(other than what normally associates with aftermarket exhaust). Not sure if this COULD be Opti or not.. just wanted to get some advice before I throw another $230 at it.
Thanks,
Jon
Instructor
Joined: Jul 2010
Posts: 152
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From: Federal Way WA
Double check your wire routing to make sure you didn't get one crossed, or not all the way on/seated...i had one plug wire not seated correctly and was getting the same thing you are describing.
Thread Starter
Instructor
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From: Chardon Ohio
New opti-spark.. just another addition to parts list the DIDN'T solve the problem. I'm really bummed out now.. Really not sure what to do now. I guess I can check the injectors, but they're about a year old from FIC. Only thing I can think of is maybe the plug wires I put on were defective? I don't know how common that is. They are Bosch 7mm and they were put on maybe 2-3 weeks before the misfire developed.
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
Opti would have been my obvious guess.
Does the problem come and go, or is it all the time, regular rhythm.
Did you look for sparking in the dark.
Check all injectors with a noid light.
Can you isolate it to a cylinder at idle
Do a compression check.
I hate to think it might be ECM related.
Does the problem come and go, or is it all the time, regular rhythm.
Did you look for sparking in the dark.
Check all injectors with a noid light.
Can you isolate it to a cylinder at idle
Do a compression check.
I hate to think it might be ECM related.
Le Mans Master
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From: Life is just one big track event. Everything before and after is prep and warm-up and cool-down laps
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St. Jude Donor '12
I don't see the ICM in your list.
Also do a search, somewhere here is a good list of the troubleshooting methods.
Also in the FSM there is a trouble tree for this.
Also do a search, somewhere here is a good list of the troubleshooting methods.
Also in the FSM there is a trouble tree for this.
Thread Starter
Instructor
Joined: Jul 2011
Posts: 166
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From: Chardon Ohio
Opti would have been my obvious guess.
Does the problem come and go, or is it all the time, regular rhythm.
Did you look for sparking in the dark.
Check all injectors with a noid light.
Can you isolate it to a cylinder at idle
Do a compression check.
I hate to think it might be ECM related.
Does the problem come and go, or is it all the time, regular rhythm.
Did you look for sparking in the dark.
Check all injectors with a noid light.
Can you isolate it to a cylinder at idle
Do a compression check.
I hate to think it might be ECM related.
Did check for sparks in the dark and found nothing.. haven't checked the injectors with a light nor can I isolate a cylinder.
Right now running 44k through it.. I'm sure I'll be disappointed.
Thread Starter
Instructor
Joined: Jul 2011
Posts: 166
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From: Chardon Ohio
The list isn't 100% complete but no I did not change the ICM. I actually just got done pricing it at Advance and I'm not sure I'm ready to throw another $110 at it.
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Drifting
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From: panama panama
check the injectors. easy test
with the engine running. umplug injectors one by one.
when you feel no diferance on engine runing. that injector is not working
by using this test I find out my injectors were bad
also check spark,
the best way to do is by getting an extra spark plug
umplug first spark plug wire and conect the extra plug. get good ground. start the car. if you see spark you ok.repeat for every cylinder.
also check your timing, fuel preasure,
hope this help
with the engine running. umplug injectors one by one.
when you feel no diferance on engine runing. that injector is not working
by using this test I find out my injectors were bad
also check spark,
the best way to do is by getting an extra spark plug
umplug first spark plug wire and conect the extra plug. get good ground. start the car. if you see spark you ok.repeat for every cylinder.
also check your timing, fuel preasure,
hope this help
Thread Starter
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From: Chardon Ohio
Well I drove the car up to Denver this weekend were it seemed to be running great.. and that's even higher elevation than here in Colorado Springs. Got the car back and now it seems to be missing even more frequently now. Disconnected each injector one by one and the engine would obviously run much worse, but could definitely notice when the other cylinder.. which ever one is it is wouldn't fire do to the jerking of the engine.
So I pulled my Pcmforless tune out and the engine actually seems to misfire even more but still not a constant misfire. Ugh!
I'm really stumped here and this is my daily driver as of now. I'll call up Advance Auto and see if I can borrow a fuel pressure tester.. since I am obviously running a little low on cash since I've thrown $500+ at this problem.
Just going to throw this in but when I pulled my tune the car instantly threw a Code 26 as soon as it started. Although I'm not completely surprised since I've eliminated the AIR pump and EGR.
So I pulled my Pcmforless tune out and the engine actually seems to misfire even more but still not a constant misfire. Ugh!
I'm really stumped here and this is my daily driver as of now. I'll call up Advance Auto and see if I can borrow a fuel pressure tester.. since I am obviously running a little low on cash since I've thrown $500+ at this problem.
Just going to throw this in but when I pulled my tune the car instantly threw a Code 26 as soon as it started. Although I'm not completely surprised since I've eliminated the AIR pump and EGR.
Thread Starter
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From: Chardon Ohio
Just a little update.. started pulling boots off plugs to check for spark and got a couple jolts out if the back-end of a boot. Called up Autozone and getting some new ones off warranty since they're only 2 months old. Will post updates tonight.
Thread Starter
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From: Chardon Ohio
Huge new lead.. an unplugged MAP sensor gives me a perfect idle! BUT I swapped mine with a new one and it was still missing. Also did a fuel pressure check. 38 at idle and 46 with vacuum line removed.
New plug wires solved nothing, also put in a new AIT sensor and had no change in misfire.
Any other ideas? I'm all ears.
New plug wires solved nothing, also put in a new AIT sensor and had no change in misfire.
Any other ideas? I'm all ears.
Le Mans Master
Joined: Jan 2006
Posts: 5,621
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From: Orlando FL
Do you have a any kind of scanner or laptop with software and interface that can look at the bus?
As the MAP voltage goes up, that will make the indication for a richer A/F. As the voltage goes down it goes leaner. By unplugging it, it should go to a leaner mixture.
At idle, back probe the light green wire (pin B) of the MAP. It should measure about 1.5 vdc. (+/- 0.1).
If that is OK, then the problem is not there and need to progress to next step.
Your fuel pressure looks fine.
AIT ?.... do you mean IAT.
As the MAP voltage goes up, that will make the indication for a richer A/F. As the voltage goes down it goes leaner. By unplugging it, it should go to a leaner mixture.
At idle, back probe the light green wire (pin B) of the MAP. It should measure about 1.5 vdc. (+/- 0.1).
If that is OK, then the problem is not there and need to progress to next step.
Your fuel pressure looks fine.
AIT ?.... do you mean IAT.
Thread Starter
Instructor
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Posts: 166
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From: Chardon Ohio
No, I don't have a scanner unfortunately. I will check the voltage when I get a chance, going to be kinda busy today.
And yes sorry I thought it was Air Intake Temperature sensor. I also cleaned up the IAC and the rest of the throttle body.. didn't seem bad. My miss was pretty bad yesterday almost seeming like it was missing every compression stroke and today since the work I did to the car last night it seems to have smoothed out a little, but still missing about every 2-3 seconds varying.
I'm thinking of facing my fears soon and doing a compression check, which won't be fun with the headers.
Thanks for your response pcolt.
And yes sorry I thought it was Air Intake Temperature sensor. I also cleaned up the IAC and the rest of the throttle body.. didn't seem bad. My miss was pretty bad yesterday almost seeming like it was missing every compression stroke and today since the work I did to the car last night it seems to have smoothed out a little, but still missing about every 2-3 seconds varying.
I'm thinking of facing my fears soon and doing a compression check, which won't be fun with the headers.
Thanks for your response pcolt.
Thread Starter
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Posts: 166
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From: Chardon Ohio
Went and got a multi-tester(meter) and will ohm test them tonight. Just for kicks I took off the vacuum hose to the FPR and blocked off both ends. When the car first starts after the idle settles it doesn't miss for an additional 5-10 seconds then it begins. Is this the computer making fuel adjustments or something? I'm still not personally convinced it's a mechanical issue.. but this weekend I will probably get a compression tester if the injectors turn out OK.
Le Mans Master
Joined: Jan 2006
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From: Orlando FL
If you pulled the injector connectors off one by one and you still had the misfire of stumble at idle, then it seems it is not isolated to one cylinder. Is this true?
If you blew a head gasket between cylinders, it might show up as a cooling problem or contaminated coolant. But you say it runs OK with power and you can usually feel something.
The ICM does not cause those kind of problems. Is usually kills the spark completely or it works. It can be heat related but when running, it usually runs normal.
Just a thought; if you had a scanner you could look at the pulse width of the injectors. I would be wondering if you had a momentary drop out.
Could there be some kind of excessive exhaust back pressure from something clogged.
If you blew a head gasket between cylinders, it might show up as a cooling problem or contaminated coolant. But you say it runs OK with power and you can usually feel something.
The ICM does not cause those kind of problems. Is usually kills the spark completely or it works. It can be heat related but when running, it usually runs normal.
Just a thought; if you had a scanner you could look at the pulse width of the injectors. I would be wondering if you had a momentary drop out.
Could there be some kind of excessive exhaust back pressure from something clogged.
Last edited by pcolt94; Jun 13, 2012 at 09:53 PM.
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Call me I'll send them right out
Thread Starter
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Posts: 166
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From: Chardon Ohio
Well guys I'm back, as much as I wanted the injectors to fix the problem.. it didn't. Back to basics. Went and got a new pcv valve and a vacuum gauge. Vacuum gauge needle holds a steady 15.5 what's going on here? A lot of my vacuum lines have been removed and capped off.