Hi MB experts,

I've searched around but haven't found too much information on this. This is on my dad's 2003 C230 Kompressor coupe. It has 53k miles on it, had service done since new mostly at the dealer with oil changes done in between by me.

He had a check engine light recently while sitting around idling in traffic, and the car stumbled. On my code reader, it pulled a code for misfire on cylinder 2. It sounds like it's a problem with the coilpacks sometimes, so I bought all new plugs and coilpacks and replaced them today.

When I pulled out plugs 1 and 2 though, they were COVERED in oil. To the point where another drop or 2 came off the electrode as I was pulling them out of the head. Looking down into the head, I can see the tops of the pistons have oil on them too. What I find strange though, is there is oil all the way up the threads too (see pic) which I thought isn't typical, as it would be the electrode area and the threads close to it that are covered in oil.

Plugs 3 and 4 were dry, and looked OK, maybe a bit dark but not horrible. I believe these are the original plugs, I don't think MB has replaced them on service A or B.

Coming from an M103 190e, oil on the plugs are typically from the valve stem seals. Is this the same issue on the M271 engine? The oil all the way up the threads of the plugs is making me wonder if the oil could somehow be coming elsewhere? Possibility of a valve cover gasket?? Maybe it's just wishful thinking...

Finally, a second picture is attached. I noticed this hose was NOT attached. It's a hose between the airbox and the head area. Is this that infamous $12 hose (which has been replaced by the dealer)? I put it back on and added a zip tie on it. Where does it go? I'm thinking PCV valve?

Any help greatly appreciated. And I found info on the cam magnet leakage and ordered the parts to fix that today. There was oil in the connectors...

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Dumb question - are you certain it wasn't overfilled?

I know SQUAT about your car and motor, but I would theorize that lack of PCV alone wouldn't cause that. But, there's an easy way to find out. Hook up that hose, clean the plugs, and see if it happens again.

Other than that, I have no useful suggestions.

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Yeah, I'm quite sure it wasn't over filled. I know that if overfilled, this car actually throws a message to tell you it is. Checking the engine oil level it states it is OK.

Yeah, I think the PCV is a completely separate issue. I have buttoned everything back up, put the new plugs and coilpacks in, and will be giving it an italian tune up as well.

Just an update:

Drove the crap out of the car at high RPMs and really pushed it, which my dad probably had not done, ever. Pulled it back into the garage and I was about to shut it off and got code P0302 again - cylinder 2 misfire. This is after the new plugs and coilpacks.

Took plugs 1 and 2 out again just to see, and no oil whatsoever - which I thought was strange.

Oh, and that second pic I posted earlier, that's the crankcase breather I'm pretty sure. It goes back to the air intake and lets the blow by get burned off later. I'll probably fit an oil catch can in between to pick up the oil, it looked like a good amount was in there.

So now it's time for a compression test. Waiting for this weekend so I have a friend to help. Anything special about doing a test on these? The electronic TBs hopefully open when you floor the pedal while cranking? I'm hoping it's not a bad head / burned valve etc.

There are several bulletins on issues with that motor. (only 3 years usage in USA)

1 bulletin pertains to "burnt valves"
others point to issues with oil in wiring harness.
also a service campaign to replace the crankcase breather hoses.

AND yes that engine does have a TRUE PCV valve that must close under boost OR oil will be pressured into the engine & also into the air intake area & damage the air mass sensor.

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Hey Doc,

I do have oil in the harness (by the front cam magnets). I have ordered new parts to replace those and they should be enroute.

There was a recall to replace a hose that sits under the supercharger I believe. That recall was done as well.

The 3rd bulletin in regards to burnt valves, is that an actual recall? From my search it seems like the issues exist but there was never an official MB recall - but more like a bulletin to alert folks that such a problem has been found.

Finally, is there a way to test the PCV valve? How hard is it to access? I'm really not familiar with this vehicle honestly so I don't know how everything buttons together. I've read up on the issues with the MAF getting oil on it. When I install the new cam sensor seals and harness I will tear down the airbox and MAF and clean it. Just from removing the filter at least, I don't see it being covered in oil.

Any tips on what I should look for would be great Doc.

Thanks.

Update:

Did a compression test on the car today.

Cyl 1: 175psi
Cyl 2: 125psi
Cyl 3: 175psi
Cyl 4: 175psi

So definitely a problem with cylinder 2. I then did a wet test, added about a capful of oil into cylinder 2.

Wet Cyl 2: 150psi

So it helped a bit, but not enough to conclusively say it's the rings. I think if it's the rings it would shoot up 40-50psi with the oil. Another 25psi might be the valves? What do you guys think? I bought a can of Seafoam and I'm wondering if I should try it out to see if that will help it out. It it indeed is a bad head, maybe I have nothing to lose by using the Seafoam?

Advice much appreciated at this point...