Jim Grant's Tech Tips
'97 Pontiac Grand Prix, Detonation, Knock and Engine Failure
Q:
I have a ‘97 Pontiac Grand Prix with a 3.8 supercharged
engine. It has a bad detonation knock when you kick in the boost, everything
has been replaced or checked. It has a new GM goodwrench engine in it.
This problem blew the last engine. The only thing not replaced was the
supercharger and exhaust. Any Thoughts?
A:
I would suggest driving
the vehicle while monitoring the manifold pressure with a scan tool. I
think you’ll find that the supercharger is over boosting the system.
I would also confirm pressure readings with an old fashioned pressure
gauge. Computer sensor values do shift/lie causing the computer to unknowingly
perform improper adjustments. An over boost condition will wipe your engine
out in no time. Other thoughts that come to mind are fuel delivery problems.
An engine that is being force fed, super or turbo charged, needs more
fuel when the pressure is on. If there’s not enough fuel, bad noises
come from the engine. Your vehicle is a real hot ride . My experience,
lots of power and reliable ride all in one package.
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