'Hard' shifting in '89 240DL

I don't know how to explain it, so here goes.

When I start my car ('89 240dl) and it's in Park (idle), the motor sounds as
if I were giving it gas. When shift to Drive, the shift is so strong, that
it feels like I'm shifting while I'm driving. For some reason, the engine
is running loudly at idle. I think the problem is that the idle speed is to
high. How can I lower it without it being so low that the car doesn't start?

Thanks.

 

Is this a US spec 240? I'm going to assume so since you haven't said
otherwise, which also means that it's fuel injected. A high idle is usually
caused by either a vacuum leak or a stuck constant idle speed valve. The
former can usually be fixed easily by replacing a cracked or split hose
under the hood, the latter you have to take the CIS valve out and clean it
out with carb cleaner to get all the gunk out of it. It's also possible
something is causing the throttle linkage to bind but this is less common.

 

I'm not sure if you have the same idle sense (throttle position) switch my
'85 765T has, but if that switch is misadjusted or the connector isn't
making contact it produces those symptoms.

Mike

 

Yes it would have that same switch, I hadn't though of that.