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Old 08-12-2003, 07:54 PM
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Join Date: Aug 2003
Posts: 18
Crappy idle/voltage protection relay?

Hi all. I am trying to sort out a car I bought on eBay sight unseen. Seller was a creep. Anyhow after rebuilding the entire front suspension, brakes, steering etc. tending to many electrical and trim issues I am left with a ****ty idle that I can't seem to cure. When not idling i.e. on the trottle over 1500rpm, it works beautifully. When on the idle program it idles at 500rpm and not very happily. There were worn and cracked hoses and I had no idea if the car had been maintained at all in the last 10 years, so just started taking stuff apart and replacing everything.

Going on the premise of a vacuum leak, I decided to basically rebuild the injection/intake system in the car. So new injectors, sleeves, o rings, air supply hoses, air duct housing, throttle position switch, gasket, the 8 rings between the airbox and intake manifold, the intake manifold gaskets, fuel distributor o ring. Also checked all the vacuum lines and replaced all the worn hoses and connectors. New plugs and wires. Essentially every rubber hose, gasket etc. plus the new injector assy's and new throttle pos switch.

A slight improvement, but still idles at 500rpm, with really jerky transmission engagement. Tach sometimes craps out but only when engine idles-running through gears it's fine. Sometimes I hear an audible click and the idle changes 200rpm.... So, I guess now we look for and elecrical problem. I swapped the idle contol unit with a spare and no change.

I figure the next part to throw at it is an over voltage protection relay, so bought that and will give it a shot. Anybody know where it is on a 86 560sl?

Any comments, advise?

Cheers, Lawrence.
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Old 08-15-2003, 01:54 PM
Steve Gutman's Avatar
Registered User
Join Date: Feb 2002
Location: Chicago, IL
Posts: 492
1. OVP is above fuse box.
2. Could be the "air slide valve" that is controlled by the Idle Speed Control Module. It should be replaced with the Idle Speed Module. The "valve" burns out and draws too much current to the Module and burns tat out too.
3. Mine had a bad Ignition Control Module. Feel it to see if it is hot. It is the silver box that goes to the coil.
1985 Mercedes 500SL Euro (Gray market)
1995 BMW 520i Euro (Gray market)
1992 BMW 525it Wagon
1994 Honda Del Sol Si
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