Dear Haasman,

I don't think it's the engine mounts. The car idles fine in park and neutral. Just when the engine is engaged in gear (D,R,L1,L2) the idle will decrease and oscillate between 500-600.

So far I've changed the following:
OVP
Spark plug wires
Plugs
Distrubitor cap
Distrubitor rotor

Reading the archive post, I was begining to believe that the problem might be the throttle actuator. But someone posted a fact that my engine does not have a throttle actuator, but instead a idle control valve. Other possible source could be the MAS, wiring harness, and vacuum leak. I'd hate to replace these things if they are not needed. Can anyone guide me in the right direction?

__________________
JR
1986 Gold 300E 4Dr automatic