99ramair

I have a 99 ls1 and when I start it the engine makes a quiet tapping noise. I have had taken it to two seperate mechanics and both have said that it is nothing big, but it still pisses me off. Suppossedly this is a semi common problem with these cars so if anyone has any suggestions i would greatly appreciate it.

EightBall

Piston slap, I have it, others have it, we all hate it.

Raise

iTrader: (31)

no, prob not piston slap. our cars are naturally a little noisy under the hood. it could be injectors....maybe lifters

EightBall

well, he mentioned it happens when he starts the car, my engine is pretty damn quiet after it warms up and the slapping noise goes away.

SSmoky01

Gm has a decarbon procedure that will get rid of the noise for about 20k miles. Basically you take your spark plugs and fill the cylinders with a specific GM chemical and let it set over night. You have to turn the engine over with the spark plugs out to empty the cylinders. Reinstall plugs and drive the crap out of it, literally. It will smoke but the smoke you are seeing is the carbon burning off. Dealership part's department will have the chemical. My bro work's at the dealership(tech) and has to do this procedure all the time for customer's. Although it is not really needed cause it is not causing any engine damage.

Raise

iTrader: (31)

actually, what u r talking about sounds like a top end cleaner that gm carries. it has the decarbon effect u r describing. basically u let it suck in through a vaccum line...wait a bit, then start the car and let all the **** smoke out of the exhaust. im doing it pretty soon before i do my head swap. i hear its good ****

SSmoky01

That procedure works too, but the proper way to do it is the way I described it, it is way more effective. My brother is a tech at a GM dealership and putting the cleaner directly into the cylinders is the right way.

bad0211secws6

iTrader: (6)

there is a bulletin to replace the oil pump sender o-ring for this knock noise.
which is common to all gm gen 3 v8s. i do this repair at my dealership quite often and i also replace all the lifters since they are under warranty. as far as carbon on the pistons i highly doubt that. i have torn the heads off probley a hundred of these motors and hardly ever see much carbon at all, even higher mileage vehicles. these gen 3s usually start this at 2,000 miles and sometimes with more miles. there is no current piston slap issues with these engines was with 97s,but iv'e never come across any since the gen 3 came out.my 02 does it right now but ill wait till i get my cam to fix it.hope this helps