I have a 2005 C230 Kompressor Sport that has had rough idle issues for the last year or so. I took it to several service centers who failed to fix or even diagnose the problem. The last service center indicated that there is a on-going problem with these engine's cylinder heads and said that the compression on the number 4 cylinder was low. Has anyone heard if Mercedes Benz is standing behind this problem via recall or similar?

 

Can you report dry & wet compression readings. The head had been redesigned by 2005 production.

You might have an erratic throttle body actuator. It won't throw a code & the only way to sort it is to replace it.

 

I don't know what the readings were, only that the compression was low.

Here's some background ...

About a year ago the car started running rough. The change was not gradual nor has it gotten any worse. It feels like a cylinder is missing or maybe an exhaust header is cracked (although I now know that probably isn't the issue). There is very little reduction in power but the engine is audibly rough and it vibrates unusually.

This may be unrelated but about a month ago the car started shuttering and stalling as if it were running on two cylinders. I took it into a MB dealer. They diagnosed it as a camshaft sensor leaking oil into a wire harness that allowed oil to flow into the ECU shorting it out. This was all covered under a recall. They fixed the ECU issue but the rough idle issue persisted. The mechanic identified the rough idle issue as a number 4 cylinder compression problem. I took it to get a second opinion since they were talking thousands for repairs. Without me telling the second mechanic the previous diagnosis, his assessment was identical. Both the MB dealer mech and the independent guy said that this was a common problem caused by a poor head design.

Strangely, the car started running smoothly again recently which seems inconsistent with a compression problem but its hard to believe it is anything else with two separate but similar diagnoses.

 

switch out the number 4 injector, coil pack, and spark plug

someone said on here he switched the injector and it fixed the head problem

 

I changed out all four coils and plugs and replaced the fuel filter. I hadn't thought about switching out the injector. It might be worth a try. Thanks.

 

If it is the head problem you have a leaking valve. If you let it continue it will burn that valve hopelessly. One thing you can try is a couple of bottles of Techron concentrate in back to back tanks of fuel & rev the hell out of the thing for a few weeks & you might blow the deposits off of the valve tulip. Otherwise it is head off and clean & reseat the valves.

Did they change the engine harness?

 

I also have a 2005 C230K 6spd (build date 05/05). Same thing has happened to me at about around 34,000 miles...CEL came on and threw up P302 code. First happened around 4/1/11 and still ran smooth except for two occasions when it ran rough at idle. It ran smooth again after restart.

I came on this board when it first occurred on 4/1/11 and swapped plugs, swapped coil packs, and error remained for Cylinder 2. Car would run smooth and CEL would come on at random times.

After the idle ran rough for the second time, I took car to dealership @ 35K miles (8/13/11). They added the wiring harness under recall. The cam sensors were not leaking though, dry as a bone.

They did tell me cylinder 2 had low compression and they would need to replace head for $4k-$5K! My ride was out of warranty and I did not get the work done at that time.

I refused to believe it was the cylinder head issue as many had said it was fixed on the 05 model years. I finally checked the compression myself with a compression tester. Results showed Cylinder 1 @ 130psi, Cylinder 2 @ 120psi, Cylinder 3 @ 140psi, and Cylinder 3 @ 145 psi. Ahh smack, the dealership was right!!

I was resigned to taking it in to get the work done and pay the $4k to get the head replaced. Before I did, I wanted to try one last thing...drive the crap outta the car and see if I can burn off some of the deposits off the valves.

I had a Vegas trip coming up and decided to drive there from San Diego. There are some good stretches of inclines that I could put a good load on the engine and run at an RPM to about 5K. I ended up getting 4 brand new plugs before the trip, a new coil pack for Cylinder 2, changed the oil, and dumped some Techron in before the trip.

I did this about 3K miles ago and I haven't had the code or rough idle since. Car has been running perfect ever since. Not sure if it's fixed or a temporary reprieve from the inevitable. I haven't rechecked the compression yet, I guess I'm too scared to check...hahah!

Anywho, I guess I just wanted to chime in and give you my story before you end up spending your hard earned cash on a new head. Make sure you check every last thing before taking it in. Like I said, I'm not sure if my issue has been fixed permanently. But it is running like new as of now. Good luck!

 

Yup, low compression on cyl 4 is the most common for this engine. I have seen this and replaced heads many times.

There is a procedure for this.

If my memory serves me right, I belive the first step is to let the engine run in park at 4000 rpm for 1 hour to "free" up the carbon. If this doesnt work, which normally does not, mechanical repair is needed.

I believe there is a DTB.

 

As best we can ascertain Benz changed to the new head from around March 2004 production.

I'm sure you managed to blow the deposits off of your valve tulips before you burnt the valve/s

Here is a Techron car's tulips.



This sort of crap builds up until the valves don't close properly & leak leading to misfires.

 

Benz used to run the engine at 5000RPM for one hour. Not a good procedure.

 

That is a pretty serious problem.

I am interested to know what causes it?.Poor engine design, poor quality fuel, short trips ?.

Is it possible to remove the carbon by the old water injection method?

 

Glyn, are those pictures a "before" and "after" view from a techron treatment?
Or are you saying, using techron regularly will keep your tulips looking shiny as in the first picture?

That sludge is horrible!

 

Thanks guys. This is great stuff. I didn't think about valve seating. I'll try techron and high revs.

 

It's mainly poor fuel quality & oil control on the valve stems. Some fuels build light fluffy deposits that blow off while others build rock hard stuff. If you analyse the deposits they are fuel & combustion by-products & gunk from from captive breathers etc. - plus burnt on VI improver (a polymer) from the oil coming down the guide. Any fuel with catalytic fines in it makes a real mess. Severely hydrocracked fuels are also a problem as they contain asphaltines. In Australia your refineries have been upgraded to Euro 4>. We are a year away. The US can't afford to take it's refineries to that level at present consumption rates & pricing. The Benz M271 engine was designed to run on Eurograde 4 or better fuels. Europe is now going Euro 5.

The water injection method can sometimes clear some combustion chamber deposits but not predictably or reliably. It will do nothing to the inlet system & valves.

Benz has excellent oil control in the valve guide area. They are used to building DI diesels.

No those are not before and after shots with Techron although they could be. For advertising purposes Chevron would generally look for cars that were even more fouled than that for clean up. I just selected them to illustrate the point.

The first pic is a member on this forum Ichibans M271 after running on Techron for most of it's life. He sent me the pic & posted it. It is very evident due to positioning of the injector in the inlet tract where the fuel can't get to clean.

Pic 2 is a US Porsche Cayenne DI engine at below 20K miles. A big problem for VW/Audi/Porsche on their new DI engines where you are injecting into the combustion chamber & have no cleaning from additised fuel.

The third pic is from a Texaco program control car running on a competitors fuel.

The M271 running on poor fuel not only fouls it's valves until they won't close properly but the combustion chamber too. A reason that you don't want to baby this engine. Rev it! it helps!

Toyota is having similar problems at present on a number of engines.

The best fuel clean-up additive systems out there at present are Chevron/Texaco/Caltex Techron & the latest from BP.

 

I'm so glad I joined this forum right after purchasing my 2005. I started using techron regularly from 25k miles and I've never babied the engine. Almost 101k miles later it runs just the same as always.

 

let us know if u change your injector and report if it worked or not

~thanks

 

It never pays to baby a hi strung 4 banger.
Drive it like you stole seems to work for me.
I notice there are people on the forum with
M271 engine with 100-200K miles who do a lot of
freeway driving and have no problems.

This tells me that yes, indeed, low rpm stop and go
traffic is causing carbon buildup.
Long runs with medium to high rpm
and the car runs fine.

Use Seafoam, it will help to eliminate the carbon and
improve compression.
I read this here somewhere, they took compression readings before and after.
It WORKS!
I suggested this to a friend, she also had the compression tested before and after, uses it regularly and it works.

 

Just please don't put Seafoam in your oil. Techron also works & is approved.

 

I've used seafoam on past cars (Camrys, Accords) but I wouldn't be comfortable with doing so on a Mercedes. I'm not sure there is any factual basis for that but I just wouldn't. If I did, it would only be in the gasoline. I wouldn't feed it through any brake booster and I damn sure wouldn't put it in the oil (no oil additives ever!).

Techron FTW, though.

 

To the OP, have you checked your throttle body? My car had a really rough idle on cold starts and it was the throttle body.

Here's my thread about it: https://mbworld.org/forums/c-class-w...-cold-cel.html

Great input on the Techron! I think I don't use it as often as I should! I fill up only with Chevron, so I figured I can do the Techron treatments every 10k miles. I guess I should go to 5k miles.

 

Not sure if anyone will jump back in 5 months after the original convo, but you sound like you found the answer. And I know nothing about cars. My C230k has only 55,000 miles. Always maintained.

My coupe has for years, once or twice a week, vibrated in the mornings, hot or cold, until I rev the engine a little. I heard this was endemic to the car so left it alone. A few weeks back, while idling in parking lots, I thought I was gonna be tossed out of my seat--that was new and frightening. CEL came on.

After dealer found 50% compression loss in cyl 2, they suggested a $6,000 cyl replacement. A mechanic friend quoted my $5k. Really? They claimed there was no or little junk built up in the cylinder. Frankly, I'm ready to sell the car--spent thousand already in last year on a service B, new brake pads, and other junk. Miss my Acura.

Is that enough info to hear someone say yes you need a new cyl or not?

 

A new cylinder? You'd come out cheaper by fitting a new engine. Although sounds like you're of the same mindset as I am, not worth it.

 

KBB says my car is worth $8500, but not with this cylinder problem. I don't even know if I could sell it now. Between a rock and a hard place. The CEL is off now, but I don't let it idle in parking lots anymore since I'm scared I'll be thrown out the window. New engine? Right. Argh.

 

I don't think you need a new engine. Maybe a new head.. but a new engine? I doubt it. At 55k miles, it is lightly driven.. do you baby it? That's the worst thing for the M271s it seems.

 

Well, maybe I can find a shop and see if machining the head will do any good, vs. spending $3k on a new head and $1-2k for labor. Who knows. Thanks for talking with me. Lesson learned--never own a car for more than 5-6 yrs in the 21st century.