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Old 08-10-2014, 08:57 AM
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Join Date: Aug 2012
Posts: 5
Question High idle in 380SL

Help please! I have a high idle in my 380SL. The idle control module was replaced by a MB dealer 6000 miles ago at a cost of $1700 (that included $760 for the module and several hours labor for 'diagnosis'). I don't want to face that again, or ever go back to that dealer. Also, when I accelerate out of a corner the engine has very little power, almost cuts out, but recovers when I ease up on the accelerator. Maybe related problems?

Maybe not connected to this at all, but my anti-lock brake light now stays on all the time (after a recent brake fluid change). Just mentioned this in case there's an overall electrical problem.

I love the car -- it has only 56000 original miles, but I need some good advice on how to fix the problems, especially the high idle. thanks

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Old 08-10-2014, 09:13 AM
Senior Member
Join Date: Nov 2002
Posts: 736
change the overvoltage protection relay and cross your fingers. it powers the idle cu and the abs also. i tell people every 8 years get that and a fuel pump relay as they don't age well and will hang you out at the wrong time. good luck, chuck.
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Old 08-10-2014, 09:32 PM
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Join Date: Aug 2012
Posts: 5
Thanks Chuck, message much appreciated. Stan
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Old 08-11-2014, 12:02 AM
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Join Date: Oct 2004
Location: Grand Rapids, MI
Posts: 15,239
With these engines age is a bigger issue than overall miles. High idle is often an overall condition of vacuum leaks. It might need all the rubber pieces on the intake gone through and replaced to get it to run properly as they are likely all dried out and hard/leaking. That is what I had to do with my 420 motor (essentially the same as a 380). Once completed, idle is very low and smooth and it has plenty of power. A properly running M116 engine should idle around 700-750 in park/neutral and around 550-600 in drive/reverse.
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 87k - mine - (OC-91,200)
'17 Metris(VITO!) - 15k - wifes (OC-17k)
'01 E320 Wagon - 159k - mine (OC-160,000)
'01 E320 - 179k - dad's (OC-182,500)
'07 E350 Wagon - 133k - dad's (OC-132,500)
'01 SL500 - 52k - dad's (OC-52,000)
'16 E400 4matic Sedan - 67k - Brothers (OC-72,000)
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Old 08-11-2014, 07:27 AM
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Join Date: Aug 2012
Posts: 5
Thanks pawoSD, we'll be sure to check out the vacuum leaks.

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