ICQ>

I've got a 1990 740, non-turbo, gas, auto trans with about 82,000 miles. I'm running 87 octane. When in gear, it seems to idle a little rough. It's

not a roughness like a rythmatic miss, but feels more like it's running on the lean side or just idling a bit slow (or fast). It sets up a sort of

rezination that can cause door panels to rattle, etc. When in neutral it purrs like a kitten. Throttle response is excellent. If the idle speed is not

right, then I would tend to think it's a little fast (about 650-750 RPM on the car's tach), as it tugs fairly strong when dropping it into gear.

Compared to my mother-in-law's 1989 740, my idle speed doesn't seem to correct with as much gain when putting in gear or turning on A/C.

Power-wise, the car goes down the road great. Given this background:

What is the proper idle speed in gear?

What is the proper idle speed in neutral?

Could octane be too low?

How does one verify/correct idle control system?

Could auto trans be trying to engage at too low of engine speed?

Could worn engine mounts cause this?

Any ideas are appreciated.

Thank You Very Much,

Chris