Motor mount issues?

[Brian Smith]

I have an set of symptoms which i have seen discussed in previous posts but want to verify before tackling. I have two or three very predictable short somewhat high frequency vibrations which shudder through my car during hard accelerations. They are not coincidental with gear shifts, but rather seem to be associated with the amount of work the engine is doing. Also, and probably related, when I am driving down the road at a fairly constant speed and let my foot off the gas, the car lurches a little. When I put my foot back on the gas a little the car lurches again. Both of these problems seem as though they may be related to bad motor mounts, but I wanted some opinions: particularly on the vibration bit. Thanks for input!

 

[sdpatt]

Rather than ask for our opinion, why not check to determine if the motor mounts have failed? This can easily be accomplished by raising the hood, setting the parking brake and starting the engine. Now gently raise the revs a bit and slowly release the clutch enough to nearly bog the engine, as if you were starting from a stop. Do this in fourth gear so that the parking brake can more easily resist the forward motion of the car.

While doing this, watch the forward portion of the intake manifold. It should not rise by more than about a half of an inch (0.5"). If the engine rises higher, your front mount has failed.

You can check the rear motor mount by doing this test with the gear selector in reverse. Observe the rear portion of the intake manifold. It should not rise by more than the same half of an inch (0.5"). If the engine rises higher, your rear mount has failed.

The transaxle mount is very robust and not subject to the loads that the front mount experiences. You can visually inspect the rubber bond of that mount from the driver side wheel well. Removing the wheel and tire and lifting the inner fender splash apron provides a clearer view, but you should be able to see if the rubber has separated from the metal portion of the mount.

 

[Brian Smith]

cool, thanks, ill check. I was more interested in the vibration, because the second problem seems intuitively to be motor mount issue. The vibration on the other hand seems stranger, almost like some sort of harmonic shivering through the car...