Vibrations at idle

[Delerious]

Background:

02 p5, 350k km's on it
5spd, runs well
rear o2 sensor code being thrown

Problem:

The car runs great, and the idle speed is nice and solid on it, right at 700rpm. The car doesn't shake at all when driving, the engine mounts don't seem to be loose or broken (yanking on the engine by hand, watching it run and there's no odd movements).

However, when the car is fully warmed up, and at idle, the whole car shakes noticeably. It's only at idle after the car is warmed up, and at its lowest idle, at 1000, 900, and 800 rpm's, the vibration is not there. There's no weird sounds or anything like that.

I figured it was the EGR valve, so I cleaned that out today, and there's no difference in the issue.

What could this be?

Thanks!

 

[slavrenz]

Perhaps a small vacuum leak?

 

[RABID_MP5]

did you clean the idle air control valve? I've yet to have to have to really learn how to do that, but you can search for it on here.

 

[Delerious]

Well I reset the ecu yesterday, it was pretty ugly before it got the idle sorted back out. It vibrates less now, but it's still there.

I'd like to clean out the IAC, but I don't know where to get those damn safety torx bits.

Also, how the hell do you work those plastic vacuum connectors? I didn't want to break any fiddling around with them, but being able to disconnect them would make things way way easier.

Thanks for the help so far!