For anyone interested in what led up to this, check out my previous thread here. After fixing a stalling problem, my 95 E300D now idles in park at 1100, and at 750 in drive. I've read many posts involving a much similar problem for mid to late eighties models. My car, unlike theirs, doesn't have an idle control valve. In following the advice from an other thread I turned my ac to max while in park to see if the rpms would increase. No change. This supposedly indicates that there is a problem with the idle control module because it is either not sensing the ac turning on or it thinks the ac is always on. I removed the idle control module and the car ran exactly the same. Does this mean that my car has been idling manually the whole time? Does this conclusively point to a bad idle control module? Where/how can I test the icm wires or even the unit itself for continuity? I had removed the ovp to test my previous stalling problem, but I'll try it again for this.

With the engine running, I began moving the lever on the vacuum box to the intake pipe just beyond the air filter. This is also the one that is connected to the throttle. Suddenly, idle dropped back to normal, if not then it was only slightly high. In trying to figure out which specific movement caused the change, idle went back up to 1100. I then moved the lever counter clockwise as far as it would go. When it reached that point, idle went back to normal again. It remained as such when I let the lever go. This worked several times. If anyone recalls from my previous thread (linked to above), one of the cars symptoms was that the idle speed would drop to about 400 in park when I turned the ac on. Well, now when I turn the ac on in park, the engine dies. No surging, no chugging at all. If it's on before I start the engine, rpms will dip, but it will catch itself. When I'm driving, if I turn the ac on, there is no significant change. Does anyone have any idea what this could be?

Today I removed the top of the intake manifold again and found a piece of plastic that was partially blocking the throttle linkage. Damn, that was simple. Now my car idles almost perfectly. But alas, my troubles have not yet passed as I am still having trouble with the ac. To be more specific, if I turn it on full blast in park, it will kill the engine. At a warmer temp setting and with a slower fan speed, the engine will die occasionally, but often times it catches itself just in time not to. Just as before, it will run fine if I turn it on during a drive. Is this a frozen ac compressor? Would it still blow out air with a bad compressor?

Is this really that unusual? I'm kind of surprised that I couldn't find more than one thread remotely similar to this. I thought it would have been one of the more common issues.

Kaiser,
After a bit of searching, I've found that if you set your climate control to economy mode, the compressor will not engage. Try that. If it ends your stalling, then you probably have seized bearings in your compressor creating a load too heavy to be supported at idle speed. Or, you could possibly have a bad compressor clutch. I believe it is possible to repair the compressor on your own, but I'm afraid I wouldn't know how. Good luck.

I have the same car, and HAD the same symptoms. In my case the problem was a defective engine coolant sensor, as well as its associated degraded wiring. Fixing the wiring, and changing the coolant sensor resolved my high idle problem.

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'95 E300 Diesel, 264,000 Miles. [Sold it]

Thanks pberku. Actually, last weekend I taped up almost every single wire in my wiring harness. Which coolant sensor is that and where exactly is it?

Is it the two-pin "Temperature Sensor for Air Conditioner Control Box" (008 542 45 17) as listed on EPC net? This is the blue sensor that from what I hear, may or may not also control the auxiliary fan. I tested the voltage on the wires for this one with the car running and got 5.02v on one wire and 62mv on the other. Is this normal? I hope so because I spent days getting to the wiring harness and taping it up. Also, I tested the sensor at 80 degrees C and received a resistance of 965 ohms. After reading other threads, this appears to be off by a lot. Am I right?

The coolant sensor is towards the back of the engine on the driver's side. To reach it you will have to remove the Intake manifold cross-over pipe. Once the cross over pipe is removed its easy to get to the sensor. The sensor has 4 wires. If I remember correctly the plug to it is a Molded plug, which I somehow opened. Once I opened it I discovered that the wired were shorted. Somehow I managed to fix the wires and put everything back. I also remember that although it has 4 wired, 2 of the wires are ground, so I just joined them together. My coolant sensor itself was also defective, so I changed it as well.

One circuit (2 wires) of the coolant sensor serves the EGR system and the Over-voltage protection relay, The other circuit (the other 2 wires) serve the dashboard temperature gage. In my case the dashboard portion of the coolant sensor was fine, but the EGR/Over-voltage relay circuit was screwed-up, and that was the circuit that caused of my high idle speed.

NOTE: The orientation of the plug is critical, yet it is round and will plug back in several ways. Make sure that you remember how it was plugged and wired so that you can put it back the way it was.

Phil

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'95 E300 Diesel, 264,000 Miles. [Sold it]

I do remember (specifically) taking out that 4 pinned plug while I was fixing my harness. It's entirely possible that I plugged it back in the wrong way. My dashboard gauge works fine though, which I guess would indicate that I have a bad sensor and/or wires as you did. I'm curious though...You said that fixing those solved your high idle. Did you also have a climate control related stalling issue similar to that of myself? I only ask because I want to make sure if I have to remove the crossover pipe for the xxth time. Since removing some debris from my throttle linkage, my idling has not gone higher than 700.

I did not experience the climate control; id;e speed related problems that you had.

One way to sort of check the coolant sensor without removing the cross-over pipe is to start the engine cold, then pull on the accelerator cable to increase the idle speed to at lest 1,500 RPM while watching the rod on top of the engine. (The one connects to the accelerator cable) It SHOULD NOT move.

Repeat this process when the engine reaches operating temperatures. At that point when you increase the idle speed to above 1,500 RPM that rod should pull on its own. If that works it will indicate that the coolant sensor is likely working correctly. If not, it likely is your coolant sensor, or its associated wiring.

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'95 E300 Diesel, 264,000 Miles. [Sold it]

I did everything just as you said, and when it warmed up the rod pulled on its own. I guess my sensor is fine then. Too bad, because that seemed like an easy fix. Something else I noticed, having to do with my idling, is that when I take my foot off the gas (ac on or off), rpms drop to about 700, hold there for less than a second, then drop to just below 500, then go back up to between 600-700 where it remains. This must mean something, but I have no idea.

Also, pberku, would you happen to know how to translate the diagnostic codes on our model? I copied this from one of my other threads: I made the code reader with the three banana plugs a while ago, but unfortunately, I can't find a code list for my model. I searched here: http://www.geocities.com/MotorCity/D.../cs1000_mb.pdf but was unable to find a code list for my chassis (124.131). Normally I would just use that of a similar model, but my diagnostic connector is very unusual. It looks like a 16-pin, but pins 3, 8, 9, 10, 11, 12, 13, 14, and 15 are empty (but clearly labeled). For the pins that are there, 16 is the voltage, and 1 is the ground. Some codes do come from the pins that are present but I can't exactly decipher them with information that says I should have pins in eight empty holes. It seems more like an 8-pin, but if that were so, the ground, voltage, and empty spots would still be in the wrong place. How do I figure out what my codes mean? Does anyone else have a 95 E300D set up this way? It would be so much easier if I could just have the diagnostic system tell me what is wrong.

Only the following faults can be read:

code cause
2 engine speed sensor L3 bad
3 ELR temp sensor bad (B11/4
6 ELR (Y22) shorted
8 ELR (Y22) open
9 control unit (N8, N8/1) faulty

I still would check the coolant sensor, and its associated plug/wiring.

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'95 E300 Diesel, 264,000 Miles. [Sold it]