Vibration

I have a 2002 Pontiac Montana with a 3.4 liter engine. While driving the engine runs very smooth (or appears too). While at a stop in drive at idle there is a terrible vibration. Sounds and feels like the van is going to come appart. Engine does not visually appear to be shaking or vibrating. Kind of sounds like a motor mount may be bad but can't verify that. Any ideas?

I would greatly appreciate any help.

Thanks

Russell

that could be the problem or the spark could be rough

I thought it could be the spark plugs so I replaced them and the wires.

Any other suggestions?

Thanks

Has the throttle body been cleaned or the IAC valve checked?

You can check the motor mounts with a pry bar, while there check the tranny mounts too.

How would you recommend I clean the throttle body?

I did clean the IAC, but have not replaced it. Would you recommend replacing the IAC?

Thanks

Russell

I have a bad vibration at idle as well in my '99. I thought it may have been plugs or wires but turned out to be a sagging motor mount (so I was told). I'm just ignoring it for now, everything else seems fine and now at 192,000 miles, I'm not sure how much longer I will have it.

I was wondering if anyone as solved the vibration issue. I have a 99 Montana and I'm experiencing the same vibration problem. I have replaced my plugs and plug wires, however I've not checked the motor mounts. I did notice this morning that the vibration would increase when the front blower was on High speed and would decrease in vibration when the blower was turned down to a lower speed.