Evidently, I have a vac leak somewhere. 91 350SDL intermittently does not shutoff w/key. Couple of searches for likely culprit founbd nothing amiss, i. e., cracked/loose tubes, etc. 'Noticed no prob so far w/brake boost, rest of cac sys, etc. Wher is most likely cuplrit; at the key switch or IP? Any tips? TIA

Could be a vacuum leak or a faulty vacuum shut off element.

Benzmac,

I agree.

Dealer tech replaced IP shut off actuator day before yesterday. Parts $44; labor $130!!!!!!!! Car in shop about 1.2 hr.

So can we assume that the problem was resolved? The shut off diaphragm on the 603 motor isn't the easiest to get at. If the guy can do it in 1.2 hours, it's one of the benefits of practice. You get quicker, not slower. The first one I did on a 300SDL in 1990 took a good me hour to figure out that the intake was supposed to come off...but I learned.
Regards,
Randy D.