AZOG

Have an S4 NA 1987

The engine shakes at idle and when I turn the AC on it gets even worse. Shifter is the most notable thing. Shakes like a mad man. Have the fancy 300 buck compression tester.

PSI at corrected rpms (After engine was driven and operating temp)
Front Rotor : 96 95 93
Rear Rotor : 99 97 99

Would engine shake be caused with these numbers? I'm thinking its the trans mount that got loose. I have new trans mount with new bushings I had replaced accouple years back. car has been driven less than 200 miles since then.
Everything is new pretty much. New clutch, flywheel, new fork , pilot bearing, new slave. NEW tps. Tested the BAC and it works. Have All emissions removed including the airpump ( S4) so don't need the pump). Also new engine mounts I installed last year that are seated properly and tight.

That one face on the front rotor is lower than the others, but could this cause shake like I am experiencing?

Any thoughts are greatly appreciated

diabolical1

iTrader: (3)

if it's shaking at idle, i would think you might be chasing a vacuum leak.

as far as mounts are concerned, did you replace with OEM or did you replace with some kind of aftermarket material (poly, aluminum, delrin, etc.). i know they should transmit more NVH, but i don't know if it would be to the extent where idle conditions would be as you describe. obviously, OEM mounts should be smooth.

AZOG

Thanks for the input . Well after engine warms up The idle bounces back and fourth in the same spot . So I know I have a vac leak somewhere but the shaking happened before that Bounce . I mean it’s driving fine and vibration gets better when driving which brings me back to the trans mount. I just wanna make sure it’s nothing major . I’m gonna check the trans mount when I install my new header next week . This entire time I thought one my rotors was fucked but after getting those compression numbers I’m thinking otherwise. Also they are oem rubber mounts for the trans that I got .

DR_Knight

iTrader: (23)

My car feels smooth as in no shaking and that’s with full solid engine and solid trans mounts.

A vibrating rotary engine sounds suspect.

AZOG

Would a loose not properly seated trans mount cause that ? I feel like that compressions good . Let’s say I do have one chipped apex seal would it cause vibration ?