I have a question for the group. I have a 91 Plymouth Acclaim with a 3.0L and about 255,000 miles. It's been a good car but it has developed a problem that is driving me crazy. When you accelerate with the car, at about 38 mph the vehicle starts to shimmy. This continues until about 45 mph at which point it goes away. You can then drive the car as fast as you like and it doesn't re-occur. The shimmy seems to shake the entire front end of the vehicle.
I've check the tires. rotated the tires, checked the CV joints and everything else in the front end and haven't found anything that could cause this. I thought I had found the problem when I found some slack (about
1/16") in one of the inside tire rod ends. I spent a Saturday replacing that (NO ROOM TO WORK UNDER THERE) and it made NO difference.The shimmy is engine speed specific. It makes no difference what gear the transmission is in (a A604 automatic) it still shimmies at the same speeds. You have to be accelerating to cause the shimmy. If you let off the gas while it's shimmying, it instantly goes away. The intensity of the shimmy is directly related to how hard you are accelerating; put your foot in it and it shimmies bad (but not for long because you go through those speeds quickly). If you gently accelerate then the shimmy is minor. Temperature also seems to affect the shimmy. When it's cold outside the shimmy is greatly reduced (although I live in Houston and we don't get a lot of cold).
I'm beginning to believe that this might be a motor mount problem. I've even thought about removing the hood so I could see the engine during acceleration to see if it is oscillating in the mounts during the time you feel the shimmy.
Anyone have any suggestions?