Engine knocking.... sorta....

I have a 96 grand am GT, and the thing sounds like it's knocking when I start it up. Give it about, 3 minutes of running time, and that sound dissapears. I usually run synthetic in my car, but the last gasket I got changed, the dude put regular in. :\

Either way, I've noticed this sound for a while now, seems to only do it in the cold tempuratures. My friends brand new malibu does the same thing, only during cold tempuratures.... is this something I should worry about? Is it causing damage if I drive it during those 3 minutes of 'warm up time' ?

Thanks.

My 93 Grand am does the same thing. As long as it runs I do not care what sounds it makes.

Any other tips? ;)

My 96 GASE makes a sound like that when i shut it off. I dont worry about it though cuz there are no other problems.

Well The noise you are discribing is Generaly To much Piston to Cylinder bore Clearence. Which is Generaly around .002 less than the thickness of one of you hairs on you head. Your friend should take his car back if it is under warrenty, Before it gets to warm and they cannot find a problem.

Welcome to the wonderful world of piston slap lol I take it you have a 3100? About 95% of 3100s and 3400s either make the sound or develop it, nothing to be worried about, as long as it goes away when the car warms up.

it could also be the harmonic balancer rubber seperating.

If it was the Balancer it would do it all the time. I dont think the 4 cyl have a balancer, they have balance shafts.

i know someone else who's got a 95 with 3.1L & it will do just like you said (only when cold, once warmed up, it's gone) - but here's the thing, it totally dissapears the moment you put it in gear (neutral still has the sound) -- and no, bringing the rpms back up while it's in gear doesn't make the sound return... it stays gone while it's in gear. i've been told it's probably a transmission problem, but since i've not heard it myself, i'd have to be weary & check around some more (does yours stop when you put it in gear?)