Compression issues & black smoke on start up

Asked by Jul 15, 2016 at 11:27 PM about the 1992 Pontiac Grand Prix

Question type: Maintenance & Repair

Ok I just had my 92 grand prix 3.1 engine
rebuilt. But...it's not running right! It's a long
story so stay with me. First it sounded like a
drag racer when it got started. Then a
cylinder had bad compression that suddenly
turned to good compression (40psi-150psi).
Also had a faulty fuel injector dumping too
much fuel. So I got new fuel injectors & got a
valve adjustment. The car sounds better but
can still hear a light pinging noise plus I saw
black smoke on start up. Now the
compression issue has returned. First it's
bad...now it's good again. Oh yeah it's not
the same cylinder doing it either. First it was
#5 then #1. Why would compression
fluctuate? Why am I still using too much
fuel? If the engine was properly rebuilt why
are these issues accruing? Obviously it
wasn't properly done. Lol. But I want my car
repaired & selling is not a option! Anyone
have a idea on what's wrong? Really
confused about the compression.....

2 Answers

30

The timing chain might not be timed correctly

4,565

If the rebuilder also installed it in your car, then I think its their problem, not yours. Drop the car off at their shop and tell them to call you when its running right. If someone else installed it then its more complicated. It could be any number of electronic or tuning issues totally unrelated to the rebuild. The engine itself might be fine, although the fluctuating compression seems suspicious. It will be up to the installer to pinpoint the problem and then you can decide how to address it. Putting a new engine in an old car is never a good idea. Hopefully the lesson you are learning won't become too much more expensive than it already has.

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