On the M103 engine in my 88 300E there are two coolant sensors near the rear of the cylinder head on the drivers side. I know that one of them is crucial input to the fuel injection system and can cause an ill idling or no idling engine. Which is the sensor for the FI, the rear one or the next to the rear one?

Does anyone have the resistance table for this sensor. I am not at home and won't be able to look in my CD until this weekend.

Thanks for any help that anyone might offer.

Larry
Here is a link to anlther post about the same topic that has the answer you are looking for.
Where's the Coolant Temp Sensor and how do I test it? '86 300E

__________________
Dave
88 300E 250K Sold
2000 C230K Totaled @104K
2003 ML320 156K Sold
2009 E350 4Matic Sport 46K Sold
2011 ML350 60K Sold
2014 GLK350 46k
2012 GL450 55K

This might help clarifying which is which.

See Benzmacs comments.

W124 coolant sensor location?

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Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"

Well according to a chart found on one of the referenced threads, mine is only reading about 50 Ohms too high at 85 C. It is reading a good bit higher at about 40 C.

My trouble is that it won't idle after starting when the engine is hot. It starts and idles fine when engine is cold, or at least as cold as it will get this time of year in Texas.

I have already cleaned the Idle Control Valve and the hoses seem fine.

Thanks for all the help.

Larry, is it only at idle that your having a running problem? and is there any change in mpg? I wouldn't think those readings would cause it to stall. Did you check the duty cycle reading since this started?

Also see this post: ICV-what's it for? and can high idle hurt trans?
From this thread: ICV-what's it for? and can high idle hurt trans?

__________________
-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/831799-post13.html
http://www.peachparts.com/shopforum/831807-post14.html

The problem ONLY effects hot idle immediately after restarting engine. After engine has been running, you can pull up to a stop, kick in the clutch and it will idle like a pussycat.

There is no fuel mileage issue that I know of and in every other way besides the hot startup idle problem it runs fine.

I'm not one to start throwing parts at a problem, but I am very close to replacing the idle valve hoses even though what I can see of them looks okay. I have not exhaustively searched for vacuum leaks since it idles so nicely when hot after running down the road for awhile.

I have not checked the duty cycle, but I will the next time I'm at home. I also will put it on the lift and see what the idle hoses look like from underneath.

Thanks for the response.