Engine Vibration


Old 12-04-03, 09:05 PM
Thread Starter
Join Date: Aug 2001
Posts: 130
Engine Vibration

I have a Jeep Grand Cherokee with a 4.0 liter engine, automatic transmission and approx 94,000 miles. The problem I have is when the car is stopped at a light while in drive and the brake on, the vibration in the car is unbelieveable. If I put the car in neutral, most of the vibration goes away. When I start driving and pick up the RPM's, all the vibration goes away. Any ideas?
Thanks for your help.
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Old 12-05-03, 02:10 AM
Join Date: Dec 2002
Location: Connetisuck
Posts: 162
These are notorious for this problem. These are unibody construction and the engine hangs down on the engine mounts. The mounts deteriorate and vibrate the hell out of you at idle even worse with the ac on. A new pair of engine mounts and a trans mount while you're at it will help this problem. Also check your manifold for cracks which usually result from this.
Old 12-06-03, 07:44 AM
Thread Starter
Join Date: Aug 2001
Posts: 130
Thanks for the response and I will check the mounts. I got anxious in the mean time and checked the torque on the front transmission band screw. Because of the location, it is impossible to get my torque wrench in, but I did notice the locknut was a little loose and I did tighten the band screw slightly. This seemed to lessen the vibration a little.

I will certainly check the mounts, but is the tranmission band tightness also a possibility?

Thanks again.
Old 12-06-03, 08:27 AM
Join Date: Apr 2002
Location: Pittsburgh,Pa
Posts: 2,417
No the band is not causing the vibration.Are you sure you don't have a misfire at idle?
Old 12-06-03, 08:34 AM
Thread Starter
Join Date: Aug 2001
Posts: 130
I don't believe so as the heavy vibration is almost nil in Park and in Neutral. That was my original guess and I changed the plugs, cap & rotor, plug wires, air filter and fuel filter and no change in vibration.
Old 12-06-03, 08:54 PM
Join Date: Mar 2001
Location: Germantown, MD
Posts: 29
Sounds like a bad engine mount to me based on the symptom. I would have somebody pry on the engine at the mounts while you sit in the driver's seat with the vehicle in gear and note any audible change while doing so.

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