I started my car tonight, and for some reason the engine seemed a bit reluctant to engage and sounded more muted than normal (hard to explain). But after several turns and a tap on the gas it started. However, it was vibrating oddly and violently, shaking the whole car, as though it were missing on one cylinder. The idle was within the normal range of 750 - 800 rpm. So I put it in drive, and it seemed to disappear. There was no problems with acceleration. I put it into neutral a minute later, and the shaking did not return. After shutting off and restarting the car a couple of times, the problem did not return.

 

What the heck happened? The first thing that came to mind was that it may have jumped a tooth on the timing belt, but since it returned to normal after engaging drive I doubt it. I'm thankful it was a momentary problem, but I'm concerned it might be a sign of something. It has never done this before.

 

Any ideas?

Okay, the car did this again yesterday. Went to start it, and I suppose I backed off on the starter because I thought it had engaged. Noticed it hadn't, resumed cranking, the cranking sounded more muted and slightly slower than normal (I don't think for lack of juice).

 

The engine starts with a bit of gas, but idles rough and vibrates the whole car significantly. As it always does after sitting for a couple of hours, the idle begins at about 1500 or so, and slowly backs down to the normal 750. I let it sit for a bit, and the idle smooths out gradually after a couple of minutes to the point where everything is fine again. I stress that it was not idling low or anything, just vibrating oddly.

 

What the heck is this? i've never experienced this in a vehicle before.

 

BTW, this does not trigger the CEL.

You said it sounded like it was running on 3 cylinders, maybe pull the wires to see. It could be running on 2 plus a little from the other 2 if the coil pack is acting up. Check that stupid knock sensor for cracks too, and maybe the coolant temp. sensor.