My Ecotec 2004 Cavalier (102k) has the occasional mega rattle when it starts. No rhyme or reason, just does it. Sounds like a lot of people have this issue with Ecotec engines, only I believe mine is louder. Just lately (within the last week) it randomly gets a rattling noise at idle. With my handy stethoscope I traced the noise (when its making it) as coming from the timing chain cover.

Tonight I pulled the cam? cover off and everything looked peachy. No slack in the timing chain, upper guide looked good, but the engine was also quiet when I shut it off to pull it apart. I zip tied the chain to both upper sprockets for safetys sake and pulled the tensioner out. From the reading I've done, it appears this engine has the old style tensioner because after I pulled it out the guts fell out of it. Supposedly the updated tensioners guts are held in with a snap ring.

I'd like to try swapping just the tensioner to see if it could have been an intermittently sticky tensioner.... but has any one ever heard of that happening? I've read lots of cryptic things on these engines in the timing department, but seeing as how this one is perfectly quiet a good percentage of the time leads me to that conclusion about the tensioner.

Does the theory hold water?

Much thanks for any thoughts.