rv93

ive had the car for going on a year now, and its had this issue from day 1. at idle, the engine shakes a little bit, but it goes away around 1k rpm or so. theres also a slight tapping noise coming from the left cylinder bank, and its a bit louder than the right bank. my first thought is that i have a sticky lifter somewhere. car currently is going on 46k miles. i seafoamed it on the last oil change, which was right after 43k miles. any thoughts?

Cam94Z28

I'm not an expert here, but I'll chime in.

As far as the shake. It could be a simple misfire. If it's not an actual engine tap, make sure there's not a plug wire on the left side that's arcing. Light tapping/ticking at idle is probably just the injectors. Could be a vacuum leak somewhere drawing in too much air. It could also just be that you're noticing the very slight lope that the stock cam might produce at idle.

As for the tap, you can also try running seafoam in the oil as directed on the bottle, or add something like valve medic, which is a detergent designed to free up sticky valvetrains.

rv93

the tapping goes away (or gets quiet enough for me not to notice) after the engine is warm. judging by its frequency, its only on one cylinder. i will definitely check the spark plug wires and see if thats the issue. i also realized it may be a bad spark plug. considering what a pain in the *** changing them is, i wouldnt be surprised if im still running the original ones. the shaking could be the lope, though from what ive read, the cam they used on the 02s was very mild. ill look into valve medic. i used seafoam last time i changed the oil, and i plan on doing it again when i change it in a couple of weeks here (was going to do it yesterday, but i recently had a motorcycle accident, and im not quite up to crawling under the car, lol. thanks for replying

Marc 85Z28

The noise you are hearing is piston slap. It's a very common LS1 noise, and per GM does not harm the engine.

The idle instability issue was covered under a TSB. GM recommends that you close the spark plug gap to .040", and use their iridium plugs. While the spark plug composition is not critical, the new gap spec IS.

rv93

ill take your word for it. i was lead to believe that piston slap would be most audible from under the engine. in my case, its all but nonexistent from there.

very useful information about the plug gap there. would the gap affect anything except idle?