OK. So I bought this car the other day, and it runs great, except for one problem. Upon cold start, it runs really rough, and if I so much as touch the gas pedal, it stalls. It takes several cranks, and then stutters like all hell. Once it warms up, it's fine. This is a completely different beast to me (coming from a W123 diesel), and I can't seem to find another post that matches my symptoms (if I'm missing something on this board, please let me know). Also, possibly related, the previous owner mentioned that the idle had been turned up a bit (warm idle @ ~2k) to compensate for a crack in the insulation of a wire going to an injector. I've ordered a part to fix that (a little replacement boot). I also plan on checking into the OVP this weekend, as the ABS light is on, and I've heard that relay can do stange things when it goes south. Let me know what you folks think. Thanks!

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1989 300E 144K

By the way, this is the part I ordered for the injector:

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1989 300E 144K

Well, first off....that part you ordered does not exist on the 1989 300E.....might as well return it.

The injectors are completely mechanical, no wires exist. Only the cold start injector has a wire, and I doubt it has any issues. The issue you are describing is caused by a faulty engine temperature sensor (at the far back of the drivers side of the engine with a big connector plugged into it) and possibly a stuck or gunked up idle control valve.

Since your ABS light is on, I'd replace the OVP relay before anything else, it could very likely be the cause of all your issues.

Your seller was feeding you stories....you can't "turn up" the idle on these cars, it is computer controlled. The whole problem is that the electronic injection and idle control system is not operating....and it is running on mechanical injection. Idle speed on mechanical injection is about 500rpm, if the electronic idle system is working then in park it should be around 700-800, and 600 in drive or reverse. And it should go to around 1100 when first started cold, then drop down after a few minutes of warmup.

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-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)

So maybe I should also be looking at an engine temperature sensor and maybe a Idle Air/Speed Control Valve . Is there anyway to test any of these parts?

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1989 300E 144K

Yes, put a multimeter that does ohm readings on the pins of the temp sensor (test the 4 pins 2 at a time, criss cross....there are two identical sensors in there for two different computers)

The idle valve can be tested just by giving it 12 volts, if it clanks and moves the little valve in the opening, it works. It'd be good to drown it in brake cleaner to get all the gunk out of it. The hoses connected between the idle valve and engine/intake are also likely hard and need to be replaced to prevent vac leaks (which might explain your 2000rpm idle)....lots of rubber parts under there, as many should be replaced as possible. Gassers are sensative to vac leaks.

Where does you economy gauge sit while in park and drive without pressing the pedal? In park with the A/C off it should be essentially pegged in the black, in drive it should move a couple need widths off the peg. With the A/C on it should move over towards the red a bit more. If its near or in the red all the time then you have some big vacuum leaks.

__________________
-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)

Economy guage sits in the black at idle. I noticed that the parts page shows two different temp control sensors, the one described above, and one at the air filter housing. Could that by chance be the one missing in this picture? Could this be part of the problem? Thanks.

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1989 300E 144K

I don't believe a 1989 model has that sensor....your intake tube may have been replaced at some point, and the later ones have a sensor there (mine does)....thus the hole. If it is not dangling around below there then I doubt yours has one. The sensor at the back of the engine is most important to the computer to run the engine properly. It needs a 22mm deep socket to be removed, and you need a proper inch-pounds torque wrench to put it in to the right torque (not much) so you don't damage anything.

__________________
-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)

Funny- my 86' is a california car- it has the 2 pin sensor- green plastic. Definately has cats.


M

It looks like there are two different versions of this plug (early version with green plastic) - one for federal and one for Cali.

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1989 300E 144K

Mine is a m103 2.6 and it is a no cat model of 1989 with the two pins on the top . I order one for the car on the registration .On delivery i found that it had a round plug and 4 connectors inside . So i had to return it for the two pin type.So looks as if they were fitted to none cat and cat modles