Engine Knock when reving engine. [Archive] - GrandAmGT.com Forum

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Tomas
08-25-2004, 06:38 PM
I am new to the whole grand am scene here. I own a 88 Bonneville and a 1991 MR2 Turbo, and my friend decided to sell his 1995 Grand Am GT pretty cheap so i bought it. Anyways the car has started to make this strange knocking noise when I rev the engine up past 2000 Rpm and then let off the gas. The noise comes on the wind down. Well I decided to see what would happen if I held the rpm range around 2500 well the knocking came consistant and you can even feel a vibration on the gas pedal everytime you hear the knock noise. I also started to notice that the car also makes the knocking noise twice when you turn it over. I really havent driven the car since the noise started to appear because I wasnt really sure what is was or what it could do to the car. Just wondering I you anyone knew what this was. The engine is the 3.1 V6
Thanks.

eric99gt
08-25-2004, 07:09 PM
hmmmm kinda sounds like the exhaust may be loose. only reason i say that is because of the knock on startup.

Tomas
08-25-2004, 07:32 PM
It does almost sound like it is coming from right underneath me but I really have not been able to see much of anything rattling in the bay, so it could be something with the exhaust. But when I rev the car up higher the knock is really loud, and it seems the longer that the car has a steady high idle the louder it is as well.

AaronGAGT
08-26-2004, 11:29 AM
Maybe you're hearing piston slap? or maybe your cat is bad? or maybe you have a marble in one of your cylinders?

Tomas
08-26-2004, 11:45 AM
Ok well I decided that I should prolly atleast take it for a little spin to see if the noise was noticable when driving. I heard nothing at all, everything ran great. Well I got back home and was like WTF. So I reved it up again to about 4,000 rpm and let it go. Well on the wind down it made a loud a$$ knock and then the car rolled slightly backwards and then rested once again in park. So with that in mind I am no thinking well is it something in the tranny. My driveway is at a slight incline so it would roll backwards, if not in park. The whole thing seems really strange to me.