I have a 1994 940(non turbo) Since the winter I have noticed that there has been a wide swing in the tachometer when coming to a stop. During the last week the problem has been prgressively worse, the tach swings between 1200rpm and say 400rpm and the engine just cuts out. It starts right up and goes but the only way to keep it from totally shutting down the engine is to keep one foot on the brake and one on the gas pedal to keep the tach at around 900rpm.
As the engine warms up after say 25 minutes it gets better but the tach still swings but the engine does not cut. However as I take off as I was in stop and go traffic yesterday due to an accident the engine sputters or drags as I take off even when warm. Thanks for your thoughts. Mike

Didn't I read somewhere before that this could possibly be brake related since it happens only when the brakes are applied? My 86 740 does exactly the same thing and I'm thinking it might be the vacuum booster is leaking vacuum and therefore cause the engine to stall out. I cleaned the throttle body, replaced the TPS and the ICV and it still has the same problem. Today I think I'll completely block off the vacuum bosster (no power brakes) and see if that affects the symptoms.

Paul

94 945
86 745 GLE

You need to check the constant idle system (CIS). First look for loose hoses to the idle control motor. It is located near the throttle body (about 1.5" diameter 3-4"long) and should have a hose from the air intake and to the intake manifold. If either has become disconnected, reconnect and your problem will most likely be solved. If not you need to go deeper into the CIS and check both the motor and the control computer. You can easily check if the CIS is working by noting if the rpm increases immediately after the engine starts. This is normal for an operating CIS. If there is no speed up then the CIS is malfunctioning. Note than this motor is expensive if bought from the dealer, so if you do need one it is best to shop around and even purchase a used one.