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Discussion Starter #1 (Edited)
1994 E320 Estate, 230,000 miles. Bought it about two months ago. Previous owner said it had a faulty MAS, and gave me a part he said included that. Not knowing what the MAS looked like on this, I took his word for it. I got home with the car and soon figured out that wasn't the MAS, but was the throttle assembly. Don't know why he had that and thought it was the MAS, but didn't worry too much about it at the time.. The problem the car had was it would idle erratically at times, not all the time. It would rev up, and occasionally die on him, mostly sitting at rest. When it would do this, it also blew black smoke. Otherwise the car ran great when not behaving like this.

It ran this way for me for a while, and was very unpredictable. It might go for days without so much as stutter, and other days be a real pain and die several times. Didn't seem to be related to being hot or cold, or any other way of predicting. I started thinking maybe it's wiring harness related. It has been getting progressively worse, to the point now that the car won't stay running, or sputters badly, with loss of power. When I first bought it, I took off the MAS, and looked it over and it looked clean and in good shape, but all I did was a visual inspection.

Other problems: fan speed is very, very erratic. Oil dummy light comes off and on randomly (just changed the oil and filter, and have been watching, it's not losing any oil - level is perfect). Power seat fuse has now started blowing instantly as soon as I try to adjust them.

Does this sound electrical / wiring harness related to anyone? I've looked around at some of the wiring ends at connectors, and I don't see any cracking anywhere, but I could do a more thorough inspection on that.
 

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'95 E300 DIESEL, '91 600SEL, '92 600SEL
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17,394 Posts
These are classic symptoms of eco junk wiring. Virtually impossible to troubleshoot until a new harness has been installed. Also suggest you buy a new genuine MB or KAE(hler) OVP relay and replace ALL fuses with the updated copper core type to establish a solid baseline.

See link for more details.

PeachPartsWiki: W124 Engine Wiring Harness Replacement
 

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1988 "Zender" 300CE Coupe, 2009 Renault Koleos, 2007 Kia Rio Sport
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3,189 Posts
+1 harness suggestion
if not then
OVP
 
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