97' SL "rumbling" idle sohc

Hello all,

I've been chasing this problem for a little while. When the car idles the engine has a very noticeable "rumble" or vibration to it. It rattles the interior panels a little and you can feel a vibration in the gas/brake pedal. The rpm is stable and the car doesn't appear to have a miss of any kind. The car starts and drives perfectly and still gets great gas mileage.

I've inspected all the engine mounts and the engine doesn't move around at all when placing the car in and out of gear. Also every once in a great while this "rumble" will even out for a couple of seconds and then it will go right back. This makes me suspect a sensor or egr valve problem.

Plugs and wires are brand new
crankshaft sensor(OEM) is new
W/P, tensioner, belt are all new
No check engine light.

I've pulled the egr and cleaned it out real good. Also I cleaned as much of the EGR passage as I could get to at the time.

Any ideas?

Check the right side top motor mount again. It's likely the cause.

Update:

I've changed all engine/trans mounts and the same vibration still exists. It recently got cold here and I've noticed this vibration is far worse at startup(cold) than at any other time. After the car has warmed up the vibration is considerably less.

Probably try changing coolant temp sensor and see what happens since it effects so many engine parameters.

Update 2::

Changed the Coolant Temp Sensor and this seems to have made some difference. Vibration is much less at cold start and after the car is fully warm, it nearly goes away completely. I can live with that since the wife drives it and she isn't worried about it. It's not really worth sinking anymore money into it. I guess these cheap little cars are okay for an "a to b" car, but the car has never really ran that well even in its best days. Not like my trusty Silverado...which has the same mileage, all parts original(even the brake pads) and it runs like a champ. Peace.