W203 C200k Coupe- Faulty Lambda?

[keithbt]

Hi, my car is late 2002 29.5 k miles when bought as cat d salvage. Minimal damage. Car not started for about 4months prior to purchase. I repaired it and had it mot tested Dec 07 and all was well. After a few months the engine management light came on. Took the car to a non franchise specialist who plugged in a laptop and said it was most probably the oxygen sensor. He did a reset and all was fine until I came back from holiday in October after leaving the car for 12 days. Almost immediately the e/m light came on again. I've not used the car much since then but this week I took it for an mot test and oh damn the emissions are way off the scale. The CO level last year was 0.15%, but this year its failed at 3.81%. lambda last year was 1.00 - this year it off scale at 0.90. Has anyone else experienced the same? The tester did mention that below 2000 revs the CO level is fine but at above this it just goes way off. Aledgedly their are two lambda sensors. One before and one after the cat. I cannot see one after the cat? All veiws & thoughts gratefully received. I like to sort these things out myself if I can,but I'm a bodyshop guy - not mechanics. Keith PS mileage now 35k.

 

[Uncle Benz]

You could have a problem with a faulty lambda sensor, but there is a more sinister problem that can affect these, where oil tracks up the wiring loom from the camshaft adjuster solenoid and gets in to the engine ecu, resulting in lambda sensor related fault codes. Sounds a bit far fetched, I know, but do a search on here.

Could still be a faulty lambda sensor though...

 

[television]

You could have a problem with a faulty lambda sensor, but there is a more sinister problem that can affect these, where oil tracks up the wiring loom from the camshaft adjuster solenoid and gets in to the engine ecu, resulting in lambda sensor related fault codes. Sounds a bit far fetched, I know, but do a search on here.

Could still be a faulty lambda sensor though...

I think to double check this excellent post,, any oil in the MAF will confirm it

 

[EwoutB]

You could have a problem with a faulty lambda sensor, but there is a more sinister problem that can affect these, where oil tracks up the wiring loom from the camshaft adjuster solenoid and gets in to the engine ecu, resulting in lambda sensor related fault codes. Sounds a bit far fetched, I know, but do a search on here.

Could still be a faulty lambda sensor though...

Thanks! This is very useful information. Have been dealing with this engine management light for some time. Initially resetting it helped for 4000kms, but recently it started going on much earlier. At the MB garage they replaced the Lambda Sensor, because they said is was broken. Cost me 500 euros. But within 200 kms the same problem. Then they fixed the connector free of change. Yet 45 kms the same problem.

Made a printout of your post and showed it to them. They said the problem is known and not only for M111. And indeed they diagnosed the problem by themselves. Now a new cap AND a new modified plug for the camshaft sensor is on order. Hope this solves my problem, am kind of getting sick of this problem.

So, MB has modified the camshaft sensor plug such that it does not pass through the oil into the loom anymore. Thought this info might be of interest.

 

[Uncle Benz]

There is a small section of wiring loom with an "oil-stop" in it which can be added in to prevent the fault occuring.

Just for reference, the problem started when they changed the type of plug around 2001. They changed from the old fashioned round pin type to a spade type connector. The round pin type are soldered to the end of the wire, so oil cannot get into the core of the cable. Capilliary action migrates it down the loom in the later type, which are only crimped to the cables. I should add that this is all based on my observations though!!!!

 

[EwoutB]

There is a small section of wiring loom with an "oil-stop" in it which can be added in to prevent the fault occuring.

Just for reference, the problem started when they changed the type of plug around 2001. They changed from the old fashioned round pin type to a spade type connector. The round pin type are soldered to the end of the wire, so oil cannot get into the core of the cable. Capilliary action migrates it down the loom in the later type, which are only crimped to the cables. I should add that this is all based on my observations though!!!!

Just had the plug and the camshaft magnet replaced today. Sofar to no avail, within 30 kms the problem surfaced again. Garage spent quite some time cleaning everything (including engine control box) with electronics cleaner. But apparently, this stuff doesn't travel up wiring looms as good as oil :-(. So they think there's still some stuff left in the wiring loom. Will now wait for 14 days and drive some kms (>200) and then have it cleaned and reset again.

Hope I'll see then end of this soon ...

 

[EwoutB]

Just a thought. Is this camshaft sensor the only point where this wiring loom can pick up oil? Or are their other sensors sticking out of the engine that might "pass" oil.

Btw, they also mentioned that oil ended up in the mass airflow sensor (which was very recently replaced).

Cant find any schematics that make indicative where this loom all goes to ...

 

[Cole@MBS]

Only the cam sensor leaks, only real cure is engine loom!!

 

[EwoutB]

What do you mean by only real cure is engine loom? Clean it (or let it lose oil) or completely replace it (which is very expensive)?

But then if only this thing leaks hopefully the leaking is stopped and it just has to lose the remaining oil.

 

[Cole@MBS]

Sorry to say it wont, as many have found out, only a new engine loom will cure it!!!

 

[EwoutB]

Thanks for your reply S-A-M / U-N-I-T.

I also noticed some oil on the block around the hose (SCHLAUCH) coming out of the block at the left front (the hose is typenumbered A111 018 29 82). From that hose something (a loom?) drops down.



Could this have anything to do with it???

Cleaned the block around the hose to see if the oil reappears.

 

[BlackC55]

I would not worry about that too much. They all do that Sir.

 

[EwoutB]

Thanks, so this couldn't drip into the infamous engine loom?

(I don't understand what the hose is for and neither the thing (loom?) that drops down from it.)

Just drove some 60 kms and see a little bit of new oil coming out of this hose, dripping downwards over the block.

 

[BlackC55]

It is a breather pipe

 

[EwoutB]

Ah thanks. But what is it used for? Ventilation of the camshaft???

And what's the loom for? Some sensor? Or isn't it a loom at all?

 

[EwoutB]

OK, never mind, it allows the oil-gases in the carter to evaporate when the engine is hot. Still curious about the loom from there. Oil level sensor?

 

[EwoutB]

Cleande it, not a loom either, just some kind of flexible tube.

Did notice fuel consumption normalizing though just a few days after the camshaft magnet was replaced.