I have recently(few weeks ago) had the same problem(engine not shutting down when I turn the key) and I dicovered it was my IP shut off valve. I replaced that, and that seemed to fix it for a few weeks. Just earlier today I noticed that it was taking a few seconds to shut off. Now it does not shut down at all. I have read that it is probably a vaccum leak but was wondering where I should start to look for the leak. I also have been hearing a "hissing" sound coming from behind the dash where the climate controls are. Could this be the leak?
Any help appreciated thanks, Dan

P.S. I have recently done some surfing on this topic and found that there are some vaccum lines behind the climate control system. I also learned that you can check to see if teh problem is back there by turning the heater on. I did this when my key was in the off position and my car was still running and the car did shut. Now that I think the problem is back there how should I go about repairing this? Thanks, Dan

There's about 5 gazillion threads on vacuum issues. That's what you're having. Surf around the board - you'll get good info.

This guy has a great little kit to get you going.

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Oro en Paz, Fierro en Guerra.

hissing behind the dash is prob a CC pod. On some models there is an orifice on the inside left-hand side of the dash between the vacuum supply line (plain yellow) and the driver's side door master valve. You can plug the yellow line up in the engine compartment, at the firewall, and most of the time the green line next to it is the CCU vacuum supply. Plug them one at a time and retry.

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1985 300D Gretchen (Astral Silver) 220k
1983 240D 4-speed Evelyn (Orient Red) 203k


TANSTAAFL

You may also want to lay some cardboard or plastic over your left carpet (including the side of the console) as a safety precaution, & pop that panel under the left dash and check the ignition switch, if you lost your shutoff pod you likely sucked some oil into the system, it is common for the short rubber lines to rot loose of the switch when exposed to oil (and after it soaks up in the insulation pad in the dash it makes a nice black streak down your carpet) and could sound like a CC pod since the switch is pretty close to those controls. I fixed mine by using some molded 90* elbows I took from a Chevy S-10 engine I had laying around, works great to this day, and fairly oil resistant since they were intended for an intake manifold.

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Chris
64 190D R.I.P.
80 240D W/617 engine -for sale
82 240D -for sale