Also, would vac leaks cause a higher or lower idle. I do notice that the transmission is shifting a bit firm...

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1989 300E 144K

The transmission should shift pretty firm, firm is better than soft. Vac leaks will raise the idle. On a throttled engine (gas) the more air it gets the higher it rev's.....that's why they have a throttle plate, it restricts air to the engine....the result is a vacuum in the intake....which is what the "economy gauge" is looking it, its essentially just showing the level of vacuum in the intake, black = high vacuum/low throttle, thus less fuel consumption, red is low vacuum/high throttle, lots of fuel consumption.

You can test for leaks by spritzing starter fluid around various spots on the engine while its running....if the rpms go up when you spray somewhere, there's a leak.

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

OK. I found the temp sensor, but it looks a bit different from anything I'm finding here (let me know if I am in error). The part that I thought I found is in the picture below (the attachment, which looks like what most other folks have). However, mine looks different. Mine looks like this:

http://catalog.peachparts.com/ShopByVehicle.epc?q=1989-Mercedes--Benz-300e-Cooling--System&yearid=1989%40%401989&makeid=63%40%40MERCEDES+BENZ%40%40X&modelid=6201%3AMBC|1507%3AED|10000013%40%40300E&catid=240909%40%40Cooling+System&subcatid=241011@@Engine+Temp.+Sensor&mode=PA

...however, it only has 2 poles instead of 3. What am I missing? All the replacements I see have 3 poles... Anyone know where I can get this little bastard?

Attached Thumbnails

 

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1989 300E 144K

This will be the component. It's usually installed in the earlier variants of the M103. Or the non cat models. It's a standard part.
Search Fast Lane - here's there part number Manufacturer: BOSCH Part Number: W0133-1615795
What's your location?

The bosch book lists these as the causes of cold start issues on continous fuel injection systems:

cold start valve
fuel pump not running
air flow sensor plate rest postion incorrect
fuel pressure incorrect
coolant temp sensor or wiring faulty

http://www.bentleypublishers.com/mercedesbenz/300e-4matic/Mercedes-W124-85-95-Workshop-Man.html

http://www.bentleypublishers.com/isbn/9780837603001/index.html

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1986 300SDL, 211K,Dealership serviced its whole life
1991 190E 2.6(120k)
1983 300D(300k)
1977 300D(211k)

Nope, that sensor is the one for the gauge on the dash. The one posted with the 4 pins is the engine computer temp sensor. It is available, its also known as the Water Temp Sensor on Fastlane:

http://catalog.peachparts.com/ShopByVehicle.epc?q=&yearid=1989%40%401989&makeid=63%40%40MERCEDES+BENZ%40%40X&modelid=6201%3AMBC|1507%3AED|10000013%40%40300E&keyword=sensor&subcatid=P:240675@@Water+Temp.+Sensor&mode=PA

A pic:

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

Sorry pawoSD, Incorrect.

Two pin version in earlier M103's. Four pin in later M103's.
Two pin version is in Non cat versions of M103. - Can use leaded and unleaded fuel.
The OP has stated that he has the two pin variety. The temp gauge sensor is a one pin in that version.
I'd be interested to know the O.P.'s location

The OP is double posting. Go to this thread
http://www.peachparts.com/shopforum/showthread.php?p=2240340&posted=1#post2240340

Sorry to double-post. I've updated my profile with my location. From here on out, I will post only to this thread, as it wil probably be more widely searched. Does anyone know what the torque specs should be for tightening? Thanks.

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1989 300E 144K