Suddenly my 1990 740,234 engine with 230k miles started idling very high,close to 1,500 rpm (Park) and around 1,000 rpm once engaging in Drive.
What can I look into/do before taking it to a mechanic? Tks

 

clean the throttle body..
adjust the idle speed...

wait for the experts to get on.

 

Sounds like the idle control valve. Whip it out and run 12v through the connectors and see if it snaps open. Could well be clogged up after so many miles so a good squirt of carb cleaner may sort it right out.

Alternatively, wait for the experts like the previous poster said!

 

I'm having this problem too. Used to be on and off when I first inherited the car... but since last night (lucky me) it's been doing this constantly! I was kind of hoping it's right itself as it's done in the past - however, not the story this time!

I've been reading online all about this problem and it's a 1986 760 turbo... I'm lead to believe that I need to clean the throttle body, so I'm off to Canadian Tire to find what I need to get the job done.

I don't know much about cars, but my father does. Unfortunately he lives 2 hours (highway driving) away... Is it a problem to drive my car for that long with such a high idle (even when in drive)?