ive done a compression test and it was 180 across all cylinders...but periodically at idle (mostly if its cold) the car will go to 1500 and bounce around there and the engin will go rrrrr.rrrrr.rrrr. in a cycle (best way i can describe the sound). The engine shakes a bit when it starts doing this but my engine always shakes because im missing a motor mount and have a blown rear tranny mount (fixing this weekend). What would cause this problem? I have never mis-shifted this car and it used to be an automatic (has 80k miles on it now)

oh i forgot to mention it throws idle air codes...nothing other than that and the usual tranny codes (missing auto tranny)

and the shaking it does is the initial movement my car does when you try to accelerate with blown motor mounts (engine rocks back a bit) and if i shut the car off..and restart it this wierd idle will go away

 

If its throwing idle air codes, id check out your IdleAirControlValve.