Once in a while when I rev my engine (in park or netural) the car will shudder at the sme time there is a thump noise. It comes from the front to middle of the car but cannot be herd in the back. Dose this happen to anyone else?

Dont rev it too high for too long as this is not good for the motor. How does the front engine mount look? Try bouncing the engine (while off) to see how much flex your getting.
Does it make this noise while driving and hard acceleration?

I forgot to mention that it happent in the 3,000-3,500 RPM range, and no I have not noticed any odd noises during normal driving or hard acceleration. I was thinking it might be something wrong with the transaxel. like it is trying to grab when out of gear. But lets hope it is not that. Ill also try rocking the engine as you had said to.

i'm not all that up to spec on our torque convertors, but that may be above the stall speed of the convertor - ie you're giving it enough throttle that it'* trying to move gears that are locked in place by the clutch packs, and the torque convertor is already eating up as much of the energy as it can.

in a word? listen to the above post - don't rev it that high unless you're in gear...

matt

My engine will very slightly shudder when in P and NOT revving it. Seems to happen when it'* warming up mostly. Not sure if it'* related to your shuddering, but I do get a lot of engine torquing and will be checking my engine mounts soon.

Don't EVER rev your engine when in park or neutral. That'* worse than aggressive driving. I agree with checking the engine mounts.

Ok thankyou for the feedback, I will try to rember not to rev the engine anymre (or at least that often). I did notice though that there is no parked rev limiter, except for redline, on my car for example I can rev it up to 5,500 RPM'* before it stops it, while a friend with a 1995 Grand Prix with a 3.1 liter engine has a limeter that will not allow it to pass 4,000 RPM'* unless he is moving. Do bonnies normally have rev limeters in that range to?

You have a problem. Your PCM may not realise you're in park. Our PCM'* have a P/N rev limiter of 4000 rpm'* also. Try pulling codes using the procedure in Techinfo, or get a scantool on the car and see if it knows you're in park.

Ok I did forget to mention that when I rev the engine the HUD and spedometer will show any speed up to 20 MPH. while the car is not moving

Do you mean the "1987-1993 ECM code retreval" peice