Hot start misses bad

[XfireZ51]

Originally Posted by Young1

Hot injector check is good. 13.6 plus or minus .1 across the group. All good per MH article.
However after hot start the miss reapoears . My timing light at idle tells a tale. But the miss moves around to different cylinders. I will check and find two with a miss then when come back around those two are fine and it is others. Appears to be ignition. What about the ground on the ECM? Possibility? Where is it?

Ignition principally has to do w ICM. I would check 14 pin connector to ICM, making sure no bent pins. Also ignition coil housing and connectors there.
I?m a bit confused by ur description of what?s happening. Are you saying that at old start motor does not miss while at hot start it does? At cold start, does it continue to run fine even after it reaches operating temps, or does it miss once it reaches operating temps?

[Young1]

Cold start. Fine no miss.
Operating temp. Fine no miss.
After a 30 minute heat soak. Misses bad. Miss will clear 5 to 7 operating minutes later.

[Subfixer]

Almost sounds like a leaking injector. Acts like an old carb motor that's flooded.

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[XfireZ51]

Originally Posted by Young1

Cold start. Fine no miss.
Operating temp. Fine no miss.
After a 30 minute heat soak. Misses bad. Miss will clear 5 to 7 operating minutes later.

So does that mean that it misses w coolant temps at higher than operating temps?

[richarde]

Another possible cause may be an intermittent fault in the crank sensor caused by being situated right next to a hot header with no circulating air to cool it. Once on the move again, air circulates and it resumes its normal operation. Being an intermittent problem, this poses it's own problem on how to test it other than trying a known good sensor.


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[Young1]

Subfixer- injectors don?t leak. Holds pressure and was viewed with plenum off. Excess fuel would burn off in 20 seconds. This bad miss goes on for minutes.

XFire - runs fine at highest operating temp when fans are running. Only on start up after a heat soak does it miss.

Richard - no headers, stock exhaust, crank sensor replaced two weeks ago when it gave me hard start symptoms. Cured that but the miss after heat soak continued.

Keep thinking gentlemen. I am going to clean 30 year old ground connections on Friday to get that eliminated.

[viper107]

What year is this car?

[viper107]

If it's 92 down with original ecm, replace it with a 95 ecm it needs it anyway

[Young1]

From XFire
So does that mean that it misses w coolant temps at higher than operating temps?

After thinking about your question a moment the answer is yes. After a heat soak the temperature would be higher than operating then after running with the fans on for a few minutes it would come to a normal temp. That makes sense.

Car is 91. Original ECM. No bent ICM pins. Coil base has all been ohm checked. I am second owner and all things were original when I bought it.

[Young1]

I called Marc H. He instructed me to get a spark tester to isolate which cylinder was missing. I bought at autozone a tester with the adjustable gap where you see the spark. I set it at a 3/4 inch opening for 30k voltage and number 2 had the miss. It?s twin number three was fine. Pulled plenum for the third time and replaced it with a known good used one. All is well. Five years ago I replaced original coils with AC Delco. Two went bad. Replaced all four 3 weeks ago with Standard Blue Streak. One went bad. I am a believer in Paul Workman?s mantra. Just because it is new does not mean it is good. Back to basics, got a miss? Get a cheap simple tester.