I have a 1986 500SEC autobox, but have a problem with the idle speed. When the engine is started for the first time of the day it runs fine. However as the car is driven, stopped and put into Park or natural the idle runs fast and doesn't drop. Can anyone tell me what is coursing this and how i can fix it.
Thanks
Andy
cheeseracer50@yahoo.co.uk

The first thing I would check out is the throttle valve switch. If the ECU doesn't receive the idle signal it will not go into idle control mode.

Lots of discussion on this in the archives.

Duke

i have a 500sel euro in the my shop right now with somewhat of the problem except for this one has a superior mind of its own.Here's all the situations it does. 1) starts, idles fine for a minute or two, idle raises, it tries to recover itself sometimes but in the long run it just dies without any hesitation.2)car starts and within seconds dies.3)while driving it stalls at all stopping points.

Done the following.
checked ovp, idle control computer, idle control valve, tried new coil, plug wires are new as is the fuel pump relay.

If there is anyone with a little help or have seen this before i would GREATLY appreciate it.

I ran the gamut. Idle speed was the Idle Speed Control Module and Air Slide Valve.

The dying (stalling) was caused by a bad Ignition Control Module in the driver’s fender well. It would run fine when cold, but after awhile it would get hot and die at idle. Mine was hot to the touch.

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Steve
1985 Mercedes 500SL Euro (Gray market)
1995 BMW 520i Euro (Gray market)
1992 BMW 525it Wagon
1994 Honda Del Sol Si