Hi there,

I'm new to this board. I have a 1987 240 w/ about 150k on it, and I've owned the car for about a year and a half. Within the last month or so, I've noticed that the engine shakes quite a bit, both while idling and while driving (more noticeable at higher speeds). The engine was also making a revving sound while idling. After reading up on this problem, I decided to replace the intake manifold gasket. I also changed the spark plugs, since they were overdue, and I cleaned out the flame trap for the first time.

The new manifold gasket seemed to solve the problem, at first. It definitely got rid of the revving sound during idling, and it drastically reduced the shaking while idling. When driving, however, the engine shake was just as bad as it was before. Starting around 40mph, the shaking is very noticeable and I can feel it shaking through the steering wheel.

My suspicion is that it's either 1) bad motor mounts, or 2) a cylinder misfire / bad fuel injector. I'm not really knowledgeable enough to narrow it down, though. Are there other symptoms I should look for that would help me figure out if it's #1 or #2? Could it be something else that I'm not thinking of?

I'm only moderately capable as a mechanic, so even if I am able to determine the exact source of the problem, I may just have to bite the bullet and take it to a mechanic. If it's something that's reasonably doable, though, I'm willing to learn. Besides changing the intake manifold gasket, the most advanced project I've done on this car is changing the timing belt.

Sorry for the long post, and thanks in advance for your help. This board is such a great resource!