Hey guys this is the deal, MB says that I need a valve job. And another guy that works on MB BMW Audi's and a bunch of other cars, says I have carbon build up. I took my car to the dealer and they charged me 700.00 to tell me I need to spend 4000.00

Has anyone had carbon build up or is that just some bs this guy is trying to feed me?

I myself have had many cars and never, NEVER had a problem like this....

Heres what happens: The car is driving fine, then out of nowhere it stutters, HARD but does not die, then the CEL comes on. The Code says that their is a misfire in cylinder 2. I have good compression in the other 3 cylinders but not the second one. As a side note if I shut the morot off and start it back up, it runs fine for miles then starts that stutter again. Anyone have any thoughts?

 

I would take it to another independent MB/BMW/Audi mechanic to have it checked out. If he says it's carbon build up as well........you should have a pretty concrete answer.

 

what years ur car, how many miles do u have on it?

i know that MBs are known for carbon build ups, but never really herd of a member having an issue with it..

 

I recently had my MB "tech" in Thailand tell me the same thing, my car has got over 100K Kilometers (lol converting that!) and was advised the same thing. He suggested carbon cleaning and also cleaning out the exhaust on the ID side from the engine (I hope I translated that one correctly lol)

Anyway, I have done the carbon clean but not the other and seems fine for now. I still want to take it in to finish up. The guy did also say its common for MBs with high mileage....

 

I had them tell me I had the same thing. Only my car made a loud squealing noise when you start it and put it in gear. I made a thread about it today. They said they cleaned the carbon off of my intake valves. Sounds fishy to me. Of course they did have the car for a week. And they still have it. When I went to pick it up, it was still making that noise! I'm trading it in soon.

 

Carbon build up is inevitable on most cars, especially cars such as Mercedes. Some way to avoid carbon build up is to use gasoline that have a large amount of detergents in them. This is why I only fill up at Chevron and Shell gas stations because they are considered "top tier" gasolines. I won't fill up at any other station because I fear this carbon build up dilemma.

More importantly, it is possible to get carbon buildup from lower octane gasoline if it does not combust as thoroughly as higher octane gasoline. The residue immediately gets stuck on the valves. This is compounded if you drive the car especially hard and don't give it enough time to warm up and driving it aggressively when the engine is cold. When the engine is cold, gasoline cannot vaporize properly (because it needs heat to vaporize) and thus you get higher carbon build up.

your best safeguard is to use higher octane gasoline with lots of detergents in them. It's usually a slow problem, but if you are careful about it every day, then the problem can be avoided, if you start now, the problem can possibly be remedied.

 

So, when Park Place offers

perhaps it's not a rip off? My car is approaching 100k mi mark and I'm wondering if I should have this done.

 

My car is an 03 c230 s/c with 79,000 hwy miles. The guy that has the car now (not the dealer) has done the carbon flush atleast 4 times with 4 seprate luqids. None of which have worked. I picked up the car yesterday and he said that the valves were clean and shiny, then about an hour later i was taking the car back to him for the same thing.

Im really sick of living in fear that the cel is going to come on at any second.

 

Is there any product you can add into the gas to help it? Like those fuel-injector cleaners?

 

So you probably got a P302 code, cyl 2 misfire. Never seen normal carbon buildup do this but anything is possible. They have these cameras, similar to what they use in surgery that can go inside the sparkplug hole and see without taking the engine apart. A normal engine with that many miles may have crud buildup but it shouldn't look like a cave with stalagmites. Most of the time, the P302 code means that you have injector issues. I would swap the injector on cylinder 2 with another one and see if the problem moves with it. Fuel pressure should be good or you would see other cylinders misfiring. 2 things cause misfires, fuel and spark. The next thing is swap out sparplugs and coil between the cylinders and see if the problem moves. It's got to be one or the other. Lastly, check compression, valve and ring compression to see if there's a problem there, maybe a cracked valve.

That takes care of the misfire but lets see about carbon buildup. What happens when carbon buildup gets really bad (not common in modern cars because they run at the edge of too lean), is that the carbon coating on everything causes cylinder head temperatures to rise above normal and cause pre-ignition (pinging). What's odd is if it's carbon buildup, why is it only in one cylinder. If you check with a camera, check the other cylinders, if they all look the same, then it's not the problem.

Remember, most mechanics are out to scam you, it's what they do best. If you find an honest mechanic, let the world know, we need more of them. Dealers are not expempt from this. There's one dealer by me that's notorious for scamming on repairs, their name is House of Imports. I would be afraid to take my car for oil change there, last time I did they wanted over $3K for repairs that were totally unecessary.

 

sound advice there, thx. I have heard though that MB here in Thailand do make their cars here rather rich to try cope with lower grade fuel

 

Hi Patrick, I think you got your facts inverted, higher octane fuel resists more to ignition (this is why some people use it if their cars are suffering from slight pre-ignition) hence high octane fuel burns slowly and might leave more deposits if your engine is not designed to work with it...

IE: If a car is designed to use, lets say, 87 and you use 93 all the time the engine won't be able to use those remaining octanes and carbon build up might happen because engine compression ratio and burning chambers temperatures are set to work with lower octane fuel, you should always use what the owner's manual states or the lowest octane fuel that lets you drive hard with no pre-ignition...

 

I concur with Buell...
The one thing I would do differently is run some STP feul system cleaner or even octane boost though the fuel system/engine for the last day before and then after you change out the spark plugs.

Do your homework on plugs. If your getting carbon, you may want need a slightly hotter plug than stock. Bosch Platinums are nice, but there are better products for the money.

 

I have seen engineering documents concerning carbon build-up in 4 cylinder engines, usually in number 4 cylinder, because of low quality fuel. DC sells a combustion chamber cleaner that you spray into the intake of a hot running engine, and then shut it off. The stuff turns to a foam. You cover the intake and close the hood (bonnet for our Thai friend) for three hours and let it soak in. Then you restart, and in about 30 seconds a lot of gray smoke comes out the back. It does not clean as well as a head off scrub, and it does not eliminate the problem from recurring.

Your first post indicates that you have a compression problem in cylinder # 2. I suppose a carbon chunk could be lodged in the valve seat, which would be quite visible on a fiber optic camera inspection as suggested by Buellwinkle. I am leaning toward a valve job from the information provided. A piston, ring, or cylinder problem is also not out of the question. You did say the dealer charged $ 700 for diagnosis, on what basis did they determine it was a valve problem, and not something else? Visible cam wear? Stem free play? I am just curious what they did for five or six hours of shop time.

 

Do you warm up your car for a long time every morning??