Merc C200 Kompressor engine codes

I bought a C200 cheap recently. Lovely car and really clean and well looked after since it was first registered way back in 2003 so I'm happy. Bought it knowing there was some issues.

So... Plugged in my OBD tool and pulled the CEL codes and get an O2 Sensor (bank 1 sensor 1) failure and all cylinders with misfire codes. The MAF has recently been changed so I'm hedging my bets that the O2 sensor is all that's causing the problem.

It drives perfectly well and MPG is spot on what the book says. The only issue is that at idle the revs are erratic sometimes - not all the time though - but it will happen every time I drive it at some point in the journey - usually after about 8 to 10 miles from what I have observed.

So my question is this... if the O2 sensor is failed/failing and idle revs cause fluctuations and sometimes even to the point that it stalls (it's an automatic btw) then will this cause the misfires in the cylinders?

From everything I've read for all cylinders to misfire is usually not a problem there but somewhere else.

I've bought a new O2 sensor which I'll be fitting this weekend but whilst I'm under the car should I be checking anything else?

My guess would be an air leak and the sensor is ok, just because the box says the sensor is faulty doesn't mean it is,
That's just an ex mechanics view though, so could be wrong.

I would mesure the resistance on the new one and compaire it
and check everything connected to the throttle body for air leaks .
strange it's not effecting fuel economy if it was lambda sensor it
usualy does.

Someone else I know mentioned about air leaks. I'll have a look at that at the same time but surely that would impede performance?

A small air leak will affect tickover and when pulling away slowly, it will be good for mpg as it's forcing a weaker mixture.

Seeing as MAF has already been changed and you have the new lambda, you might as well fit it. Watch out - you often need a special deep socket with a recess for the lead from the sensor, normal deep sockets will not work.

If problem still remains, sounds like air leak. Find a mechanic with a smoke machine and ask him to smoke test your inlet and the leak should quickly become apparent.

Quote:

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Originally Posted by Over Carl

Seeing as MAF has already been changed and you have the new lambda, you might as well fit it. Watch out - you often need a special deep socket with a recess for the lead from the sensor, normal deep sockets will not work.

If problem still remains, sounds like air leak. Find a mechanic with a smoke machine and ask him to smoke test your inlet and the leak should quickly become apparent.

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Yeah that's what I was thinking. It can't hurt to change it. I have the tool to change the O2 sensor already and a nice new torque wrench. I also have a smoke machine from my old business that may be what I need. I'll have a go over weekend and report back.

Could still be a MAF fault if a non genuine has been fitted, cheap after market sensors cause lots if problems. Just because it's new don't assume it good.
Had a similar fault on an audi when I scoped the lambda it's was intermittently going up to near 3v, the sensor in question should go run between 0 and 1v turned out the new sensor was a lucas brand. 💩

this was sent from tapatalk if it makes no sense...

I'm not a mechanic but I dabble wherever possible to save money for me and the relatives and everytime I've seen those codes on my reader it has never been the maf or 02 sensor, I've always found a airleak in a perished rubber pipe, normally a Vaccum pipe somewhere and not easily spotable because it's been underneath the pipe as it were ! so have a good look around all the small rubber pipes and you might find something.


Regards

So after checking things out a bit more and doing a bit of research it seems that there is a vacuum hose from the supercharger that perishes and tears at the one end. £10 for a new one but it's a bitch to get to due to Mercedes putting lots of things in the way.

So to test it I think I can get to it with my hands easy enough - the damage always seems to be in the same place (There was a service bulletin in the US but not done in the UK) - going to try wrapping with some nice thick hardware tape to see if it makes any difference before progressing. Shouldn't cause any problems should it? If that works then I'll replace it.

This is baffling me now. Went to change the O2 sensor that was complaining and realised my torque wrench aint fitting where it needs to be so moved on to the next step - checking the vaccum pipe mentioned in my last post. First up - remove the air box to get at it. OK.. So they put these Torx T20's in a place that you just cannot reach with a conventional screwdriver - ARGH! this is infuriating.

As part of the process of removing the air box I had disconnected the MAF (Which hasn't been giving any codes out) and after reassembling the air system I forgot to reconnect the MAF. Didn't realise until I started the car up to make sure it still actually worked.

oddly my idle revs appeared to be okay. Thought I must have pushed something on tighter when reassembling the air intake.

Plugged the OBD in and MAF error. WTF! I thought. Had a look and realised the MAF was disconnected... Plugged the MAF back in and code goes away but idle is rough again. So I disconnected it and left it like that. Idle is fine now - MPG and performance don't appear to have taken a hit but I'm still getting the other codes.

Going to get an adaptor so I can undo the other screws on the airbox later and hopefully give it another go to get at the pipe but right now I'm thinking the MAF was to blame all along! Luckily ECP are doing the original Bosch for £101 at the moment :)

I'm still hedging my bets on a Vacuum pipe somewhere ! as I said before, the error code I think is P100 is a generic code and it doesn't give any direct component failure indication, there all related, Maf sensor, 02 sensor, ingectors etc and they will all throw up that generic code ......... at the risk of sounding boring and repeating myself, I will anyway, I have never found one of those components to be faulty when reading that fault code and there expensive items to swap out, so unless you have exhuasted your search for that elusive Vacuum pipe, which is not always visible, I had one that was split on the underside of the pipe and looked normal once, it wasn't til you flexed the pipe that you could see the split, then I would carry on looking before replacing expensive parts.

Quote:

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Originally Posted by Lestronics

I'm still hedging my bets on a Vacuum pipe somewhere ! as I said before, the error code I think is P100 is a generic code and it doesn't give any direct component failure indication, there all related, Maf sensor, 02 sensor, ingectors etc and they will all throw up that generic code ......... at the risk of sounding boring and repeating myself, I will anyway, I have never found one of those components to be faulty when reading that fault code and there expensive items to swap out, so unless you have exhuasted your search for that elusive Vacuum pipe, which is not always visible, I had one that was split on the underside of the pipe and looked normal once, it wasn't til you flexed the pipe that you could see the split, then I would carry on looking before replacing expensive parts.

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We can land a man on the moon but can't detect where a failure is really happening lol. I guess to do that we would need so many more sensors than is practical that it's not worth it. Hope it's the pipe as they are a tenner. I'm crossing my fingers and my toes. :)


Sent from my iPhone using Tapatalk

I remember having some great fun and games with another w203 kompressor that I never got to the bottom of (although that one would barely start, if I got it warm then it would run at about 400rpm and did nothing when you pressed the pedal).

That pipe you mentioned is a good thing to check (I assume you are talking about the one under the air filter?)

If that doesn't yield a result, it might be worth smoke testing it. Will cost a little bit of money, but that is the only way you can confirm your inlet is leak tight before throwing more money on parts.

If your scanner lets you view live data, it could be worth connecting the MAF, clearing fault codes, then hopefully you can watch the MAF value gradually rise with RPM. Normally if car runs better with no MAF that points to bad MAF, but there is still possibility of an air leak being the real culprit.

Quick crude check is to put your head under the bonnet and listen for the hissing/whistling noise of air. Sometimes you can't hear the noise over the rest of the engine noise, but yesterday I was lucky I found a split vacuum hose on a Touran in approx. 2 mins just by listening and looking at pipes.

Your comment about pinpointing faults is spot on - many people assume that workshops plug in a magic computer than pinpoints the fault. However the codes we pull out of control units are better considered as crude assumptions that give us some direction. You are spot on that to get fault codes that would pinpoint the problem would need shit loads of sensors everywhere which would add a lot more cost and complexity. Also I believe the actual "logic" in ECU's has been gradually evolving where newer ECU's have a much larger list of potential fault codes so hopefully fault code is more targeted.

This bit is hopefully totally irrelevant but I thought I would mention it. I'm guessing yours has M271 (black top) engine? Look at the two camshaft actuators (the two round thingies at the front of the engine at the top). They are known for dribbling oil into the wiring loom which then wicks along the loom and causes all kind of crazy issues. If you look at the actuators, there should be a small cable plugged to each (approx. 8 inches or so) and this cable then plugs into the car's engine wiring loom. If the loom plugs direct into the actuators and doesn't have the cables inbetween, get hold of them if you intend to keep the car for long. If oil gets into the loom, car can end up with loads of apparent electrical issues with the engine and a workshop that doesn't specialise in Mercs would probably change a few bits before getting no joy and giving up (after having burnt your cash pointlessly).

Unfortunately I've been too busy to follow this up. The car runs okay (Idle is a little rough but it doesn't cut out) with the MAF disconnected. I do indeed have the M271 and am aware of the oil issue which is also on my list of things to do.

At least I got my Pioneer installed last night though :)

Well I still haven't gotten around to sorting this out (Had two deaths to deal with :() - Anyway, MOT is due in a few weeks. Engine light is still on but this should get marked as an advisory. It has a rough idle with the MAF connected still but been driving it at 32mpg average since disconnecting it some time ago.

Will the car fail if the engine light is on and the MAF is disconnected? I need to find a garage that will run an emissions test for me but am hopeful it is within the range.

I got off my arse finally and had a look at this (MOT next week). Removed the air box and lo and behold there was the pipe. 1 inch split up it. So - first of all taped it up to see if that made any difference - nope the tear was folding in on itself so wouldn't let air flow through. As I didn't have the replacement part to hand I cut off the last couple of inches of the pipe and stretched it into place. All seemed okay but I was still getting MAF/O2/misfires.

Ordered the part - £8 delivered. Fitted it today in my lunch break. The one end was a piece of piss to fit but the other end was in the most awkward place ever. Not so much of a problem to remove as it turned out that the other end had perished so much it was no longer connected LOL! Managed to jam the new one on but can't put the clip back on at the difficult to reach end. Need a different tool I think but it's secure enough for now. reconnected everything and took her for a 10 minute spin. After a few mintues the engine management light disappeared.

So after all that and a quote of over £300 from Mercedes I did the repair for £8 - even bought some new tools to get it done which is always nice :)

Thanks for the advice everyone. I'm going to get the rest of the hoses checked at some point but right now the important thing is getting it through next weeks MOT.

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Originally Posted by EvilBoB

I'm going to get the rest of the hoses checked at some point but right now the important thing is getting it through next weeks MOT.

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Smoke check is the way forwards. This easily shows if any point is leaking.

Today I found a faulty breather valve on an Audi A4. Car had been to a place that I think are very skilled/have brains. They saw fault code for air leak, but their customer was insisting not to pay for diagnostic costs, and just wanted his lambda sensor changed.

My mate thought it most likely was a lambda problem so happily changed the lambda but the fault still existed, so he performed a smoke test before the car left his hands, so at least he would have better info for if/when the customer was willing to bring the car back and pay diagnostic fee. He checked the car with his worker and they both believed the intake was leak free.

I went down there today and found the breather valve was very slightly leaking which was the real cause. Without the smoke tester, no amount of inspection would have ever found the issue.

Please note I am not talking about the MOT smoke check, but another type of check where smoke is fed into the air intake of your engine while the engine is not running, and the idea is to see where the smoke escapes from.

So here I am one week down the road. Things are pretty good. Passed the MOT but every so often I'm still getting a random misfire that causes the CEL to come back on. It goes off again just after the next start. I'm guessing that something else has perished under the hood. Need to get it looked at when I get a bit more time but I'm happy with it for now. It's only come on twice in the last week and I've done about 1000 miles.

Do you have obd2 to read the codes a cheap one will do from eBay and use torque . It not great but it has all the pids for the
What you need

Suspect the HT leads and the crank shift sensor