As most of this year M104 or M111 engines, my 220E had to get the wiring fixed because it was breaking the insulation all over the place.

The first sign of breakage was in the MAF sensor plug, the wiring near the plug was very stiff and when I had to remove the MAF sensor for a spark plug replacemente, I felt the wiring break inside. Since then the engine would work erraticly, misfiring, etc.

I took a deep breath and decided to tackle this project: disassembled the ETA, intake, etc. and removed the wiring, wich was rebuilt with new plugs and pins, as well as new wires, by a very experienced automotive electrician. Since the MAF sensor plug is sealed (non-rebuildable) I got a used one with a very good wiring condition and mated it to my "new" wiring.

When re-assembling the intake received a new gasket and the injectors were installed with new o-rings. The wiring was installed and the engine fired right up, but I noticed the following:

- When firing it up, the idle surges for about 2 times, climbs to about 1800 rpms and then slowly descends to the normal cold idle (slightly under 1000 rpms).

- As the engine gets to the normal working temp, the idle slowly climbs up to about 1200 rpms and stays there if the car is not moving. If you release the brakes and let it roll down the road, the idle will almost imeaditly get down to 800rpm or so (considered normal idle). When you stop the car, the idle will get up to the 1200 rpm again and stay there.

- When the car is not moving (idle at 1200 rpms) If I apply a small load to the engine (i.e. turn the steering wheel to the right or left and keep it there) the idle drops to the normal rpms range (aprox. 800 rpms) and stays there as long as Im holding the steering wheel to one of the sides.

- When the idle is high, if I put the transmission in Drive (auto) the idle will momentarly go up about 200 rpm and only then engages 1st gear. (This must not be healthy for the tranny, thats why I stopped the 220E and I'm currently comuting with the 230CE.)

- The LED code reader consistantly points to a faulty MAF sensor (4 blinks).

Until now, I've checked if all the plugs are correcly connected, checked for the (visible) vaccuum lines for cracks and leaks (would appreciate if anyone has a vaccum diagram for a M111.960). The engine performance appears to be normal except for when accelerating from stoplight, when it misses a bit but quickly regains power.

I've also replaced my MAF sensor with a used one from a friend's 220E (same p/n) but the symptoms were still there.

What I tried today was to start the engine with the MAF sensor plug disconnected. The idle surge when starting the engine disappeared, but the engine was still missing when accelerating from a standstill.

I'm leaning towards:

- a vaccum leak that I'm missing somewhere (when the engine is cold, I suppose the ECU sends a constant signal for enrichment of the fuel injection thus compensating the excess of air not measured by the MAF sensor)

- something wrong with my MAF sensor and/or plug, providing faulty values from the MAF reading to the ECU (I've checked the 4 pins on the MAF plug and all seems OK).

I love my 220E and its probably the most fun W124 I've driven... ever. My parents have a cabrio W124, I have a C124 and I love these cars but this situation has me stumped!

Any help / input is greatly appreciated...

Where did you get that code ?????????

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A Dalton

LED code reader plugged on PIN #8...

It blinks 4 times and stops. I can delete it, but it pops up again after starting the engine.

Suspect could be un-metered air ...check the pipe from the MAF to the intake..make sure the intake air temp sensor is plugged into that pipe and that the clamp on the intake side is tight.

I would also clear the memory on that pin 8.

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A Dalton

It really looks like air is going in without being sensed by the MAF.

Is it possible to damage a MAF sensor (or even worse, damaging the ECU) by shorting the wires on the plug? I ask this because the engine was started when the wires were broken on the MAF plug...

Clear the memory on that pin...you want to get adaptations back to zero so you know that is not why the code re-appears.

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A Dalton

Hello Arthur,

I've cleared the codes on all pins before but the MAF sensor code is always there after I start the engine.

I am currently looking for vac. diagrams so I can go through every single connection and eliminate that possibility.

Also going to re-check the pin connections from the MAF sensor plug to the ECU plug.

I've got 3 possible faults:

- MAF sensor failure
- vaccum leak / un-metered air
- ECU / wiring fault

Thanks for all your help.

Miguel R.

All that you have done is to clear the code..then you start the car and the code comes back....so, I want you to clear the MEMORY in the ECU back to Normal.

After you clear the code and get a Single blink, then wait 2 sec, hold the button again for 6 sec..then turn key off for 10 secs , On for 10 secs , and then start the car...Now you have a cleared memory in the module...otherwise you have to run the car for a bunch of drive cycles for it to self re-adapt.
Your ECU memory is out of spec from the prior repair.
You are confusing Code clear and Memory clear...nothing to do with one another, except the CE module sees an out of wack memory/fault at the Module, so it just keeps popping the code. So, clear the MEMORY>>>>>

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A Dalton

Oh!... Gotcha now!

Will report the results later tonight!

Thanks once again!

Well, did exactly what you sugested:

Read codes; 4 blinks.
Erase code and re-read; 1 blink.

Press the button during aprox. 6 seconds, turn ignition off for 10 sec., turn ON for 10 sec and start engine.

The start was rough as usual (idle jumps up and down 2 times and then settles) and driving it didnt reveal any change at all.

Havent check for codes again since I just arrived home and gotta go to sleep. Will let you know tomorrow.

Did you check the MAF wiring end to end? i.e check for continuity from MAF plug to termination at ECU. I had similar problem when one the wire form MAF sensor was broken near ECU.

You can find the wiring diagram here http://www.autolib.diakom.ru/CAR/Mercedes-Benz/1995/C220/SYSTEM%20WIRING%20DIAGRAMS/5301.pdf

P.S: C220 uses same engine as E220.

If you are comfortable with rigging your own interface try,
http://www.peachparts.com/shopforum/showthread.php?t=236925&highlight=HFM+scanner

You can monitor all parameters that DAS can.

Will re-check the wiring between the two plugs tomorrow! Also, brought the vaccum pump from the workshop so tomorrow will be test-day!

I am considering buying the Carsoft cable kit to use with that software...

I dont wanna give up on my 220E!

Quick question: Does the M111 has a cold start valve, like a M102?

Found the problem.....

The wiring harness became brittle and shorted the idle switch connector on the ECU.

This MELTED the pin 18 that comes from the socket to the circuit board. It doesnt look like it burned the board, I'll just have to plug it in and try to see if its permanently damaged.

I'm in the processo of rebuilding the main ECU plug on one end of the harness.

Lets see how this works out......