grober
MB Master
You will have to post a picture of your engine since what you say seems very unusual?? Is your air cleaner on top of the engine or at the side?
1994 E200 W124 idle problem when hot
marcintosh
Member
I will take some pictures this coming weekend. This is the engine with the air filter box on the left hand side of the engine bay.
grober
MB Master
Maf Position
I take it you mean the offside(drivers side on RIGHT HAND DRIVE car) when you say left side of the engine bay, since left and right varies according to whether you are looking from the front or rear of the car. Sounds as if thats the later type of injection system on the twin cam 111 engines. Heres a picture of the position of the MAF on an W124 E220. Its a cylindrical unit with a multipin connector just after the aircleaner box. The air then passes across the engine to the throttle body via the flat plastic inlet pipe.
I take it you mean the offside(drivers side on RIGHT HAND DRIVE car) when you say left side of the engine bay, since left and right varies according to whether you are looking from the front or rear of the car. Sounds as if thats the later type of injection system on the twin cam 111 engines. Heres a picture of the position of the MAF on an W124 E220. Its a cylindrical unit with a multipin connector just after the aircleaner box. The air then passes across the engine to the throttle body via the flat plastic inlet pipe.
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marcintosh
Member
Yes, sorry, driver's side. On your left when you're lifting the bonnet.
Mine is quite similar but instead of the MAF element, there is a piece of plain plastic pipe. At first me and the guy at MB thought that the car has been modified in some way but after consulting with a senior technician, it turned out that such setup as mine was manufactured for 6 months in 1994.
I'll post some pictures this weekend to illustrate what exactly it looks like.
Mine is quite similar but instead of the MAF element, there is a piece of plain plastic pipe. At first me and the guy at MB thought that the car has been modified in some way but after consulting with a senior technician, it turned out that such setup as mine was manufactured for 6 months in 1994.
I'll post some pictures this weekend to illustrate what exactly it looks like.
marcintosh
Member
Finally got the pictures. As you can see, a pretty normal engine but no MAF.
Dave Lewis
Active Member
I just nipped out to look at mine ('93 200 pre-facelift). It's exactly the same as yours.
There is a sensor with a vacuum line on it just before the throttle body though.
There is a sensor with a vacuum line on it just before the throttle body though.
grober
MB Master
WEIRD, it would be nice to have a closeup pic of the throttle body area to see if there are any differences there. I assume the ECU needs some measure of the volume of air entering the throttle body. There is also what looks like a rectangular control unit?? on the nearside inner wing just behind the abs unit which might be part of the system?? another picture? Its roughly in the position of the older w 124 ezl ignition control unit
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This engine uses the Bosch PMS (pressure management system) rather than the HFM (hot film management).The airflow is measured in the throttle body.
These M111 engines ran till august 96 in the C-class when the switch to the MAF system occurred.At the same time the coils moved to a position over the spark plugs and the inlet manifold design changed.The upshot being the 1997 M111 02 engines used slightly less fuel and ran a bit better.The ECU's also changed to integrate with the new electronic 722.6 5 speed gearbox.
Sorry I came late to this thread I could of saved you a bit of time.If you still have uneven idle when hot check the crank sensor,the signal from these Hall type sensors can intermittently cut out due to the copper winding around the magnet breaking down with age and cracks expanding when hot.If you have not already done so disconnect the battery for 10 minutes,this can sometimes clear a confused ECU.Things like the Lambda probe and coolant temperature sensor also need to be working for the car to idle smoothly.
adam
These M111 engines ran till august 96 in the C-class when the switch to the MAF system occurred.At the same time the coils moved to a position over the spark plugs and the inlet manifold design changed.The upshot being the 1997 M111 02 engines used slightly less fuel and ran a bit better.The ECU's also changed to integrate with the new electronic 722.6 5 speed gearbox.
Sorry I came late to this thread I could of saved you a bit of time.If you still have uneven idle when hot check the crank sensor,the signal from these Hall type sensors can intermittently cut out due to the copper winding around the magnet breaking down with age and cracks expanding when hot.If you have not already done so disconnect the battery for 10 minutes,this can sometimes clear a confused ECU.Things like the Lambda probe and coolant temperature sensor also need to be working for the car to idle smoothly.
adam
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grober
MB Master
A picture of the PMS ecu here.http://www.carelect.demon.co.uk/pic10.jpg compared to the later BOSCH HFM type. http://www.carelect.demon.co.uk/pic9.jpg
IMD
Active Member
Regeneration valve - cure for rough idle
This post seems to be a bit old, however I'll add my thoughts!
I've been experiencing similar problems on my 1993 e220 estate. In Drive or Reverse, the revs fluctuate between 500 and 750, sometimes quite eratically, other times not at all. I took the car into an independant Mercedes specialist today and he ran a full diagnosis with the ECU, as well as spending a couple of hours checking over the car.
He has found that the regeneration valve is not working and this, he thinks, could be the problem, rather than the MAS. When he initially disconnected the vacuum lines from this valve unit, and played around covering and uncovering the tubes, the revs fluctuated in the same way. His suggestion is to replace this and see if it cures the problem. I'll let you know what the outcome is later next week. £75.00 including fitting seems cheaper than a new MAS!
This post seems to be a bit old, however I'll add my thoughts!
I've been experiencing similar problems on my 1993 e220 estate. In Drive or Reverse, the revs fluctuate between 500 and 750, sometimes quite eratically, other times not at all. I took the car into an independant Mercedes specialist today and he ran a full diagnosis with the ECU, as well as spending a couple of hours checking over the car.
He has found that the regeneration valve is not working and this, he thinks, could be the problem, rather than the MAS. When he initially disconnected the vacuum lines from this valve unit, and played around covering and uncovering the tubes, the revs fluctuated in the same way. His suggestion is to replace this and see if it cures the problem. I'll let you know what the outcome is later next week. £75.00 including fitting seems cheaper than a new MAS!
