Quote:
Originally Posted by zonefive
I've noticed that the vibration only occurs when there is a load on the engine at idle, by placing it in drive or reverse with the brake on, and when that happens the rpms drop about 75 from 780 to about 705, and occasionally into the 650-700 area when the AC unit clutch activates, and the vibration gets much worse.
Are the rpms supposed to drop that much when the engine is engaged/loaded by the transmission?
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The RPMs may drop that much (I have a manual so I don't know exactly, but that sounds right) but that may not be causing your vibration. The engine mounts act as a band-pass filter, transmitting vibrations in certain RPMs but not in others. The engine mounts, especially ones that are faulty, worn out, or just cheap, transmit vibrations in the low RPM ranges. The engine is making the same vibrations as any other RPM, but at lower RPMs they are just transmitted to the cabin better.
Power steering pump getting a load (by turning the wheel when stationary) or turning the AC on, or putting it in D or R with your foot on the brake, these things will all lower the RPM.
You said you replaced them already, what brand did you use? Also did you replace the transmission mount? (I think there is only one on top of the trans)
I concur with Fifty150hs, I would double check the engine mounts -- I have had cheap brand RockAuto engine mounts that were bad the moment they came in the mail (for other makes). I would also agree that you could try raising your idle speed to try to alleviate the problem.