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Topic: M104 idles low when cold Reply to Thread
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  Topic Review (Newest First)
11-23-2016 10:34 PM
valicaddy I will answer my own question:

It was the protection relay (OVP).

I replaced it with a good used one and car starts at 1300 rpm, after few seconds goes down to 1100rpm and stays there until it warms up then slowly drops. Also idle doesn't drops rapidly anymore between gear changes. Great people and great source of info on this forum!

Thank you everybody !
Regards from Romania.
11-23-2016 12:30 AM
valicaddy @sbaert : I am now sure throttle body is OEM but it works fine and wires feel smooth, not like the ones w/o insulation (checked in a junk yard on a filthy W220)
@Earl.Allen : You got away cheap. Mee too, as you'll see below.
@LeftCoastGeek : 4 wires or so; good thing is wiring is fine and thanks for the info about ECT! I was looking for that! Not too late to cancel the order I placed for a new sensor.
@Trevor Hadlington : my thoughts exactly but no, not this time.

But we all forgot the Boogie Man! Me first! Who is he when we are working on a W124?
11-22-2016 10:35 AM
LeftCoastGeek the ECT (engine coolant temp sensor) is easily tested with an ohm meter. warm the engine up, unplug the ECM, and test it at the ECM plug while the engine is still warm, wait for it to get cold, and test it again. if its anywhere close to spec, its good. ECM connector 2, resistance between pins 28 and 36. With the engine hot, it should be a value like 200 ohms. with it at 20C/68F, about 2500 ohms. 0C/32F, like 6000 ohms.
11-22-2016 10:02 AM
panzernacker Would a replacment engine temp sensor help .It send a message to the computer that engine is hot .But is running cold .I could be stuck .Then computor thinks its at normal working temp ,so then no enrichment
11-22-2016 08:31 AM
LeftCoastGeek yeah, thats a throttle body we never saw on this side of the pond. without CC, it probably has fewer wires than our CC/ISC version.
11-22-2016 06:47 AM
Earl.Allen My wife's car (1993 300CE w/M104.992) had this same cold-idle stumble as well as a non-functioning cruise control. I replaced the throttle assembly with a unit built in 2001 and all the symptoms disappeared and the CC now works. I found the unit on eBay for $399 and bargained it to $325 with free shipping.

Edit: BTW- Your post is the first I have seen with a symptom exactly like mine, and I looked extensively. I was going to refrain from asking the forum members until I eliminated the eco-junk components... now I don't have to ask!
11-22-2016 12:51 AM
valicaddy Here:
11-22-2016 12:32 AM
LeftCoastGeek can you read the mercedes part number on it? that would be a XXX XXX XX XX number immediately after a mercedes logo. the CC/ICS green label module is 000 141 57 25, like this...

11-22-2016 12:16 AM
valicaddy I understand.
blue labeled 95M06 so I gess it's OEM (car is 1995).
Later today I will start the engine wiggle things a little and see if there is a change. I will report back.
11-21-2016 10:24 PM
LeftCoastGeek the hard part of doing your own rewiring is access to the right grade of wiring with the right color codes. otherwise you end up with a bundle of undocumented ugh, and make life miserable on yourself or the next guy who has to look at it.

be sure to use the correct gauges of automobile grade oil resistant wire as its a filthy hot environment in the engine compartment. CC/ICS has like 11 pins connected, using a mix of 0.5, 0.75 and 1.0 mm^2 wiring. Inside the CC/ICS, there's a motor, a solenoid, and 2 potentiometers, along with some limit switches.
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