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  #16  
Old 03-10-2016, 10:37 AM
KarTek's Avatar
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Location: Bahama/Eno Twp, NC
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Not sure which sensors are required to start/idle.

I know the normal sequence of things to start the engine when the key is turned is this:

1. SOV opens (click sound)
2. ECU cycles rack full on ("tok" sound) and should drop back to a position about 6mm forward of "closed" or full aft. This is the idle position. 1 and 2 may occur simultaneously.
3. During cranking, the ECU will slowly advance the rack forward/more fuel until it senses the engine has started. Once it senses the engine start, it will instantly drop the throttle back and maintain idle.

That's the way it SHOULD work.

This is a good reason to remove the side cover so you can observe the rack movement during start up. It's also a good excuse to replace the gasket on the side cover...
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  #17  
Old 03-11-2016, 03:01 AM
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Join Date: Feb 2016
Posts: 21
Problem Solved

Replaced the upper engine wiring harness and all is well!
I can't quite believe it but I've tested the old harness and whilst there is not shorting between the pins I found two non conductive connections to what I think is a temp sensor! I have the OM606 non turbo and the sensor in question has 4 pins and is located on the back right side of the head.
I can't find any other fault with the loom so can only assume that these two bad connections were causing the ECU to tell the IP to run on full throttle???
This could have been really dangerous had this happened whilst driving.
I've attached an image of the sensor location (the one wrapped in grey tape was the problem sensor). Could any one confirm that this is a temp sensor??
Attached Thumbnails
W210 OM606 runaway diesel problem-img_1169%5B1%5D.jpg  
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  #18  
Old 03-11-2016, 08:17 AM
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Not sure if I should post a new thread so please advise if I should....
I've solved the runaway problem and now the car starts and idles ok for a short while then the idle becomes a little erratic.
I've scanned the car and have errors with the ICS (I think this is the Idle control switch?) so I'm guessing that's why there is a problem with the idle? , a stop light error and an air intake temp sensor error. The air intake temp sensor was missing when I got the car so I know this needs replacing! Where should I start looking for the stop light error? Could this just be a bulb replacement?

I'm getting a reading for the RPM but the tachometer isn't registering anything.
The heating is also blowing hot even when on a cold setting.
The Coolant temp on the instrument panel is rather hit and miss and seems normal then shoots right up and then returns to normal.
Could the ICS and tachometer be connected on the same fuse? If so does anyone know where I should start looking to try and fix this?
Thanks in advance
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  #19  
Old 03-11-2016, 11:03 AM
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Start looking for ground problems if you have several unrelated symptoms. The brake light is likely a bulb or socket and might not have anything to do with the other symptoms.
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  #20  
Old 03-11-2016, 06:46 PM
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Location: Columbia, SC
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These cars are notorious for the brake pedal switch failing.

There are two contacts in the switch, one makes when the pedal is pushed (and the pin extends), this turns on the brake lights
The second contact breaks when the pedal is pushed. This goes to the ECU and prohibits more than idle power while the contact is broken.

Easy peasy to change out and not too expensive.
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  #21  
Old 03-12-2016, 03:13 AM
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Thanks again for all the help guys. I don't have a lot of experience with Mercedes so the experience of the people on here is a massive help.
Whilst checking the fuses I found that someone had used the wrong fuse in the fuse board beside the battery (under the rear seat). Position 7 should have been a 7.5 but someone had use a 4 and it had blown! Changed it and I've got my tachometer back! Nothing I've researched online or on the fuse holder guides says that this fuse should be related to the tachometer!
So I've still got a rough idle (starts and idles fine at first but then surges a bit). Anyone know where the ICS (Idle control sensor) lives on these cars??
Also the heater is still blowing hot air when on full cold! Anyone got any idea's where to look for problems here? I'm reluctant to think it would just be low refrigerant in the A/C as surely that wouldn't cause the air to be hot but hey ho this car has a mind of it's own so guess I can't rule that out!
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  #22  
Old 03-12-2016, 03:18 AM
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Oh I've noticed that I've got a vacuum line that's not connected anywhere! If I suck on it it opens the butterfly valve on the air intake. It's about a meter and a half long so could connect to almost anywhere in the engine bay!! It is connected at one end to something under the expansion tank but I've no idea where the other end is supposed to connect. I can't see anywhere obvious where this should be but perhaps that's causing my idle issue.
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  #23  
Old 03-16-2016, 01:15 PM
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Quote:
Originally Posted by LanzaroteSteve View Post
Oh I've noticed that I've got a vacuum line that's not connected anywhere! If I suck on it it opens the butterfly valve on the air intake. It's about a meter and a half long so could connect to almost anywhere in the engine bay!! It is connected at one end to something under the expansion tank but I've no idea where the other end is supposed to connect. I can't see anywhere obvious where this should be but perhaps that's causing my idle issue.
That sounds like the resonance butterfly used to vary the length of the intake, if so there is a valve block linking the two together (two butterfly valves).

On the OM606 fitted to the W124 it's bolted to the underside of the intake manifold.

Regarding the erratic idle, re-attach the five earth points under the hood.

These can rust and give all sorts of issues, give me a shout if you need the location points - fairly easy to spot as small clusters of brown wires held with a single bolt to the tin.
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1996 Mercedes S124 E300TD - 129k - rolling restoration project -

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  #24  
Old 03-16-2016, 02:38 PM
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Sorry, didn't see babymog's post suggesting earth points too.
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1996 Mercedes S124 E300TD - 129k - rolling restoration project -

1998 Mercedes W210 300TD - 118k (assimilated into above vehicle)
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  #25  
Old 03-16-2016, 07:29 PM
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Take a picture of the starting point of this unhooked vacuum tube and I'll see if I can't find it on my car and trace where it goes.
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