# Extreme Carbon Buildup at 90,000 Miles



## Bster67 (Nov 2, 2006)

My '07 Eos has just over 91,000 miles on it and about a week ago my check engine light came on. Took it in Monday, dealership garage says fault codes show engine is misfiring. They look at the engine and there is a bad carbon buildup, which they will clean (for $660). I get a loaner for a couple days, they call back and say that the carbon buildup is so severe that a portion of the engine would have to be sent out to another company for an "acid bath". That, with some other items, would cost about $3,500.

This is a car that has been driven primarily highway miles, always had premium gas, and has had every recommended scheduled maintenance. When I asked why the carbon buildup occurred he had no explanation, just that fuel can build up deposits. When I asked if I did spend the $3,500, would the problem come back, he said he couldn't guarantee it wouldn't.

I had them do the cleaning they could do (for $700) and picked up my car. Now, according to them, "it's just a matter of time" before I run into trouble. I've loved driving my Eos for 4 years, but now I'm seriously considering trading it in very soon. This was my first VW and I think it will be my last. Have any of you heard of this problem? Any advice? Thanks!


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## BsickPassat (May 10, 2010)

it is a problem with most direct injection engines.

you have PCV, plus some exhaust gas from valve overlap and no fuel to wash the valves... which leads to the build up.


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## solarflare (Mar 28, 2007)

The type of gas that you use or your maintenance habits have nothing to do with this problem. The deposits on the intake valves are cause from oil vapor from the crankcase. The PCV system vents crankcase gases to the intake manifold so that these gases can be burned thus lowering emissions. In normal engines gasoline will keep these intake valves clean because the gas is injected before the valves. The detergents in the gasoline actually clean off the burnt-on oil vapors from the intake valves. As mentioned earlier Direct Inject engines inject the fuel directly into the combustion chamber which bypasses the intake valves. This increases fuel economy but leaves the intake valves to fend for themselves. I'm afraid we all (all Direct Inject Engine owners) have this to look forward to in the future.

My Eos was acting up at 40,000 miles. Cold mornings would produce misfires and rough idles until it warmed up. After having my rings replaced because of an oil consumption problem I got a free valve cleaning as part of the repair and she is idling as smooth as she did at day one.

Some owners are adding a oil catch can to their PCV system. This is basically a can filled with a material designed to condense the oil vapor out of the PCV gases before entering the intake manifold which in theory should reduce this build up. Others are using a product called seafoam which is a detergent that is injected into the intake manifold and design to clean the intake valves. I haven't seen any proof as the effectiveness of these ideas. You can read more about this topic over in the Technical 2.0t forums. 

I would do the $660 cleaning and leave it at that.


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## just-jean (Sep 14, 2006)

i like the $10 seafoam treatment once a year :thumbup:


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## Bster67 (Nov 2, 2006)

Thanks for the information solarflare. If I understand you correctly, it is the design of the system that causes the problem. What I was led to believe was that it was pretty much a random occurrence. They wouldn't just say that this is a problem that I could expect to happen. 

Either way, after several problems with the car, I have lost trust in it. It's getting traded in within the next few weeks and I'm on to a new ride.


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## DavidPaul (Nov 28, 2009)

*Good Luck Finding Another New Car W/O these Problems*



Bster67 said:


> Thanks for the information solarflare. If I understand you correctly, it is the design of the system that causes the problem. What I was led to believe was that it was pretty much a random occurrence. They wouldn't just say that this is a problem that I could expect to happen.
> 
> Either way, after several problems with the car, I have lost trust in it. It's getting traded in within the next few weeks and I'm on to a new ride.


I have been following some other forums that are discussing these very same problems, including Cadillac, Audi, Porche and Ford, just to name a few.

All are having problems with carbon build up with direct fuel injection engines when the mileage gets a little high.

Seems this is going to be the nature of the beast until the manufacturers figure out what to do.

In the meantime, make sure you do not purchase a vehicle with direct fuel injection. You will get a little less MPG and a little less power, but it may be worth it. 

With the older, standard fuel injection engines, we could just take our vehicles out and blow the snot out of them. This will not work with the Direct Fuel Injection vehicles.

Sometimes, the newest and brightest technology fails us. Blame the EPA. The pressure put on manufacturers is enormous and perhaps more than they can handle.


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## Hybridowner (Dec 3, 2009)

DavidPaul said:


> I have been following some other forums that are discussing these very same problems, including Cadillac, Audi, Porche and Ford, just to name a few.
> 
> All are having problems with carbon build up with direct fuel injection engines when the mileage gets a little high.
> 
> ...


 Lexus has a v-6 engine with injectors in the intake manifold and the cylinders. Problem solved.


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## Boosted2003! (Mar 10, 2009)

Meth injection is always not a bad fix to this problem.


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## BsickPassat (May 10, 2010)

Boosted2003! said:


> Meth injection is always not a bad fix to this problem.


Meth injection still leads to the buildup


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## DavidPaul (Nov 28, 2009)

Hybridowner said:


> Lexus has a v-6 engine with injectors in the intake manifold and the cylinders. Problem solved.


I cannot afford a Lexus.


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## BsickPassat (May 10, 2010)

DavidPaul said:


> I cannot afford a Lexus.


But you can afford a $40,000 VW.... you can get a Lexus IS for that money with the Toyota D4-S system


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## Boosted2003! (Mar 10, 2009)

Boosted2003! said:


> Meth injection is always not a bad fix to this problem.


 Not as bad since it has fuel going through the intake ports.


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## Megaroo71 (Oct 23, 2012)

*EOS with 38,275 miles*

My engine light came on and I took it in and they told me the same thing about carbon deposits... at 38,000 miles! 
I previously drove a Jeep and in the 5 YEARS I had it it was only in the shop for routine maintenance! They did a good will repair for me, and yet this morning (the next day) my engine light is on again. I am very concerned that this could be an ongoing problem... has anyone had it happen more than once after having it cleaned? The dealership service told me to only run premium gas and I should be fine.


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## deltaP (Jul 26, 2011)

I have not seen the question, but does this happen to the 3.2 motors also OR is this just the 4 cyl turbo's?


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## [email protected] (Oct 26, 2012)

deltaP said:


> I have not seen the question, but does this happen to the 3.2 motors also OR is this just the 4 cyl turbo's?


This will happen to all engines that have direct injection. Any engine that has a fuel injector inside the combustion chamber.


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## Cintoman (Feb 20, 2010)

*Passat 2.0T with 34K having this problem*

Had my '10 Passat 2.0T Komfort Wagon sitting in my garage for 5 days. Started it up and it was idling roughly with the CEL blinking. I rev'd it a bit to smooth out the idle, and eventually the CEL disappeared and the car started idling fine. Didn't go anywhere with the car and just stopped it.

The next day my wife took the car, and after starting it, it started idling a bit rough. As she drove away the CEL came and stayed on the entire day she was driving it. The next day it didn't come on. 

I still took it to the dealership where they diagnosed it as having the carbon build-up. Because it was late in the day, I had to schedule an appointment for next Friday (1/11/13) for the "de-carbonization". VW of America is covering the work, but if not, the Service Manager said it would likely run me close to $600 for the job.

I bought my Passat new 35 months ago, and it only has about 34,200 miles on the clock. Can't believe I'm running into this issue so early.

Despite me running only Shell 93 octane gas from day one, and going thru all the Free Scheduled maintenance work at the dealership, the service manager said the problem is with the oil companies not putting in the same amount of detergents they used to put in. Apparently, during the Bush years (and I'm not making this political), he passed some law that allowed the oil companies to reduce the amount of detergents they have to put in their gasoline. Because the price of gas was going up dramatically during this time (2008 or so), detergents added significantly to the cost of a gallon of gas. So by reducing the required amount would likely lower the price of gas. Well that law is still on the books as no one felt it necessary to repeal this law and put things back to how it used to be.

He did mention that Shell and Chevron still add detergents (everyone see the Shell magazine ads showing scientists holding a dirty valve alongside a clean one), but not as much as they used to.

I'm just glad VWoA is covering my car, but pissed that this will be happening to my car in another 34K miles or so again.

-- Cintoman


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## BsickPassat (May 10, 2010)

doesn't matter what gas you use. fuel is not sprayed onto the intake valves


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