Just a couple days ago my '01 S2 started making a strange noise.

It sounds like a "BB inside of a coffee can shaking." I heard from a friend that this could signal detonation?! Also another Fffed up fact is that I found my oil cap off my damn valve cover just the day before! luckily it must have been off for just a lil bit b.c there was minimal oil on the valve cover. Well I put a couple quarts back in to where it would read @ a normal level (b4 it was readin closer to Lo) SO I also bought a new oil cap from advance auto or somethin and it still makes the noise sounding like it's coming from the cams?
I'm thinkin that b/c of the crappy oil cap from advance w/ only one rubber gasket on it is allowing some of the synthetic oil blend to seep through at high RPMs (it doesnt leak @ idle w/ hood up )

As far as mods are concerned, I have AEM V2 cold air intake, HKS cat-back Hipower exhaust, DC sports header, and a gutted cat; in that order.

Now keep in mind that i've had my cat gutted for over +4 months and my check engine light has been on (had it read for catalytic failure) so i'm pretty sure it's not from the ECU readin too rich b/c i've reset it after the mod and it's been soo long since i did it, right?? Well needless to say I'm thinkin about having the ECU sent off to be reflashed to the closest curve for my modifications. Any POSITIVE suggestions would be appreciated.

Thanks guys!

 

If you didn't find the old oil cap under the car, this is what's making the noise. It has fallen down between the back of the engine and the firewall and has become lodged somewhere on top of the tranny casing. Get a coat hanger and go fishing.

The subject of missing oil caps have been around since the car came out.
Here's thread I did to help you understand what may have happened:

https://www.s2ki.com/forums/index.php?showt...hl=lost+oil+cap

 

I've heard that when catalytic converters go bad they sound like BB's rolling around in there. You mentioned that you had some cat work done?

 

well i hope you're right xviper, right after work I'm gonna go fishin for the oil cap!

 

Xviper