My 1990 240 is idling real high. Unplugged aic and idle dropped below normal. No vacuum leaks no intake hose leaks between maf and throttle body. Cleaned throttle body. Car is a 5 speed.

 

It could be your throttle body is worn out and leaking through the butterfly axle shaft, or the butterfly is misaligned in the throat. The engine can't idle high unless it's getting air. It's coming from somewhere, and it's going through the MAF. Could your throttle linkage be binding or out of adjustment?

I'm not sure which one is which, but some of the older cars had a simple idle adjustment screw. It didn't use a throttle regulator like newer cars.

 

Thanx .. it ended up being a bad mas air flow sensor previous owner bought a cheap one off internet and it lasted 4 months. I had just got car last month.