More Ignition System Fun-Tempurature Intermittants
02-10-2013, 09:00 PM
#1
Safety Car
Thread Starter
More Ignition System Fun-Tempurature Intermittants
So in the on going intermittent misfire saga of my 93 I'm going to try and see what the collective minds of CF come up with based on what I know.
Previously car would misfire once hot above 180 only at idle if it was started with coolant temps below freezing. If you left it sit and cool back down to say 130 or so it would fire right up and run till hot again and never miss at all. If it was above freezing out I never had any issues.
Keep in mind this was only at idle. Rest of the time car ran just fine.
Today, I started the car inside the garage with coolant temps at 46.
After 180 or so it started to misfire, I had an inline checker on the coil and could see it not having spark. I let it run till 228 when the fans kicked on.
I shut it off and let it sit for a while. I went to restart it and the coolant temps where about 160 or so. Car wanted to start but the best way I can describe it is, it kicks and bucks like its trying but wont catch. (Acts like its out of time-really). It did finally take off with some opening of the throttle, just cracked it a bit.
Let the car warm back up and NO misfire past 180 at all the whole way to 228 with fans on.
I do not understand this at all. Its kinda crazy.
I did some testing and this is what i found.
We can rule out a lot of things because the car does run.
1.Low res. signal from opti on my scan tool is 100% all the time and at idle 22ms on the read out.
2. High res. signal counts from 0-255 like it should 100% of the time. So we can assume the Optical Portion is working.
3. AC voltage at white wire on ICM from ECM (timing control from ECM wire) reads 5.56AC volts at idle. (FSM wants you to check for AC volts to be 1-4 when CRANKING at white wire). AC voltage went up with RPM increase. (This is interesting because FSM page 6E3-A-72 says IC signal voltage should be between .5-4.5 volts. I saw as high was 12V AC.
4. Misted everything today with water and no change.
Last year I put new thermal grease on the ICM because it had none Gone after 20 years. I also tried a new ICM (just plugged it in) when it was doing its misfire thing last year, no change. So I left the stock on it. Returned new ICM. Car never gave me any trouble after it the weather warmed up in April so I let it go.
Definitely seems to be temperature related.
My gut wants to say I might have a cap and rotor issue, but I hate to tear into it for that without any proof. Car runs fine under load and such. Just hot at idle, sometimes....
Same goes for ECM, ICM, Opti-Spark, I have no proof of any of them NOT doing their job. All test come back ok, as far as voltages and things go. I do wonder about the ECM signal to the ICM if that is accurate. If anyone wants to test theirs and find out. I would be grateful to know.
Your thoughts/comments?
Previously car would misfire once hot above 180 only at idle if it was started with coolant temps below freezing. If you left it sit and cool back down to say 130 or so it would fire right up and run till hot again and never miss at all. If it was above freezing out I never had any issues.
Keep in mind this was only at idle. Rest of the time car ran just fine.
Today, I started the car inside the garage with coolant temps at 46.
After 180 or so it started to misfire, I had an inline checker on the coil and could see it not having spark. I let it run till 228 when the fans kicked on.
I shut it off and let it sit for a while. I went to restart it and the coolant temps where about 160 or so. Car wanted to start but the best way I can describe it is, it kicks and bucks like its trying but wont catch. (Acts like its out of time-really). It did finally take off with some opening of the throttle, just cracked it a bit.
Let the car warm back up and NO misfire past 180 at all the whole way to 228 with fans on.
I do not understand this at all. Its kinda crazy.
I did some testing and this is what i found.
We can rule out a lot of things because the car does run.
1.Low res. signal from opti on my scan tool is 100% all the time and at idle 22ms on the read out.
2. High res. signal counts from 0-255 like it should 100% of the time. So we can assume the Optical Portion is working.
3. AC voltage at white wire on ICM from ECM (timing control from ECM wire) reads 5.56AC volts at idle. (FSM wants you to check for AC volts to be 1-4 when CRANKING at white wire). AC voltage went up with RPM increase. (This is interesting because FSM page 6E3-A-72 says IC signal voltage should be between .5-4.5 volts. I saw as high was 12V AC.
4. Misted everything today with water and no change.
Last year I put new thermal grease on the ICM because it had none Gone after 20 years. I also tried a new ICM (just plugged it in) when it was doing its misfire thing last year, no change. So I left the stock on it. Returned new ICM. Car never gave me any trouble after it the weather warmed up in April so I let it go.
Definitely seems to be temperature related.
My gut wants to say I might have a cap and rotor issue, but I hate to tear into it for that without any proof. Car runs fine under load and such. Just hot at idle, sometimes....
Same goes for ECM, ICM, Opti-Spark, I have no proof of any of them NOT doing their job. All test come back ok, as far as voltages and things go. I do wonder about the ECM signal to the ICM if that is accurate. If anyone wants to test theirs and find out. I would be grateful to know.
Your thoughts/comments?
