All of the stupid things check out OK: the oil filter is on, the oil lid is on, the oil pan plug is in, the oil level is fine.

It sounds like something smacking against plastic. I thought that maybe I had set something on top of my alternator and it was smacking against it at first.. but that wasn't it.

Then I thought maybe I dropped something in the valve cover, but it's coming from the bottom of the car, really.

The sound follows engine speed. it doesn't matter which gear i'm in, or if i'm in neutral or park. It gets quite loud at about 1000 rpms, but dissapears or is drowned out by the engine at 2000+ rpms.

It really sounds like it's coming from between the oil pan and tranny oil pan. there is a plastic cover there, right next to the oil filter. What is under that cover anyway? something moving? I wonder if something is smacking against that cover. I probably nudged it a lot while getting the filter off.

The car is a 91 RS 305 TBI with about 110k miles.

 

i believe the cover you are referring to if the flexplate cover...im not sure how an oil change would effect it.....

 

It could be from a loose spark plug... worth a check.

 

if you somehow knocked the flexplate cover out of place it could be hitting the flywheel....just a guess.

i'd really think the flywheel would of knocked it back eventually though. take a look...

 

Oh. Yep. It's the flexplate smacking the flexplate cover.

I bent the cover inwards it while removing the oil filter.

Thanks for the help, guys.

 

Glad you found the problem, I thought it was a self-tapping screw.

 

lol