i have a 91 deville that sometimes it will start and run fine. other times it will start but run very ruff blowing black smoke out the tail pipe. sometimes it will start and run down the road for a mile then start cutting out.durring the time that it starts and idles so ruff it will not set a code. i have pulled the throttle body and cleaned it and the pipes, replaced the plugs with delco, replaced the tps, idle motor and set them, cleaned and checked the egr and replaced the map sensor, checked for vac*** leaks. i have put a fuel gauge on it and durring the time it runs ruff the fuel preasure holds steady at 36 pounds. the last time i drove it after setting the voltage on the tps/idle motor it set a p47, lost data between the ecm and bcm. i am out of ideas.

ORIGINAL: Ricklh

i have a 91 deville that sometimes it will start and run fine. other times it will start but run very ruff blowing black smoke out the tail pipe. sometimes it will start and run down the road for a mile then start cutting out. during the time that it starts and idles so ruff it will not set a code.

i have pulled the throttle body and cleaned it and the pipes, replaced the plugs with delco, replaced the tps, idle motor and set them, cleaned and checked the egr and replaced the map sensor, checked for vac*** leaks. i have put a fuel gauge on it and during the time it runs ruff the fuel pressure holds steady at 36 pounds. the last time i drove it after setting the voltage on the tps/idle motor it set a p47, lost data between the ecm and bcm.

i am out of ideas.



the key term here is BLACK SMOKE !

1. coolant sensor ? the computers think engine is cold and trow too much fuel at it?
2. have you checked each fuel injector? all it takes is one to be stuck open.
3. also, the fuel pressure seems a bit low but I dont think that is it.


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my buddies caris doing the exact same thing. I know hes thrown a bunch of parts at it, plugs, sensors, fuel filter, etc.. any headway with this? If notwe'll let you know what we come up with. Seems like our problem has to do with spark/ignitition. Lots of backfiring. . . hes blown up two mufflers.

The oxygen sensor and the coolant temp. sensor work together to come up with the fuel mixture parameters if either is not functioning properly you will get a rich mixture at the injectors.

ORIGINAL: digitalsolutions

my buddies caris doing the exact same thing. I know hes thrown a bunch of parts at it, plugs, sensors, fuel filter, etc.. any headway with this? If notwe'll let you know what we come up with. Seems like our problem has to do with spark/ignitition. Lots of backfiring. . . hes blown up two mufflers.



The 1st post made no mention of backfiring and blowing up mufflers. Sounds like raw fuel is pouring into the engine, then flowing into exhaust - this is different than the 1st post. I be checking leaky fuel injectors, spark timing and cam timing on this one. Now, a combo of all that AND coolant sensor AND oxygen sensor could COULD also be an issue.


For the 1st post, Ricklh, I be testing the coolant sensor. If that is OK, test oxygen sensors next. Just like the two prior recommendations.


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