Our 87 760 Turbo has 140K miles. and VIBRATES in idle but the tach still shows a steady rpm. We have done much work to no avail. remove and cleaned intake manifold. replaced: plugs, wires. distributor cap,timing belt,crank pully. Finally we took it into a foriegn car repair. He verified air mass sensor OK. and adjusted the throttle body. Now the vibration is ALMOST gone BUT in park it idles at 1500 rpms and in gear drops down to 900. When adjust idle down to 800( while in park) and put in gear it vibrates again but idle remains at 800.

IS this RIGHT? When in park and I rev the motor to 3000rpm the idle returns down to 900 and then when shift to gear it remains at 900. Put in gear and tap just a little bit and idle returns up to 1500.

Repair man says it's an older car and will idle high. Is this right?

We have an appointment to bring car back to mechanic in 3 days. He says he'll take a look at it may take 5 hrs diagnosis time.

What gives?

any ideas?
Thanks in advance
Brian