biggsie

Check engine light came on this a.m. I'm under CPO so I brought it into the dealer and they are saying the cylinder walls need to be "decarbonized". Now, I know you're probably chuckling but I actually paid to have this done 10k ago at the dealer's recommendation at the 60k checkup. The car is relatively new to me and I figured the cause was bad gas and driving habits of the previous user.

The dealer is actually going to do this second round free of charge (I don't want to tell you what the first one cost). Dealer then called back to ask if I've noticed any oil consumption. I have - about 2 qts low at last change.

Question: CPO runs out in 6 months so I want to cover everything that I possibly can. Could an oil leak within the engine be causing carbon deposits on the cylinder walls?

I tend to use my car for some short trips around the city but I do plenty of runs up to Tahoe which I would think would burn off the carbon.

Thanks in advance.

MYD-WGN

Audi did that 20 yrs ago with walnut shells.If every thing is right you should have no problems

Nappy

How the heck do they decarbonize the cylinder walls???

SpeedTriple

Steam cleaning. Water in, crud out.

SpeedTriple

Is your allroad running rich? Carbon deposits also result from unburnt/improperly burned fuel.

MYD-WGN

There is no way you can have carbon build up on cylinder walls.Valves maybe

biggsie

...they say it's build up on the cylinder walls. I agree it sounds very odd.

They also confirm that my mixture is spot on. Not too lean nor too rich.

Anyone want to vote for an oil leak? I was 2 qts low during my last change. Haven't noticed anything on the floor of my garage.

More importantly: is this covered under CPO?

Trango

reminds me of an old timer trick. google > ["carbon deposit" "vacuum hose" water]

SpeedTriple

And on the top of the pistons.

biggsie

Got the car back. Since I paid for this service last summer, Royal Motors was kind enough to:
- Redo the cleaning (whatever it entails)
- Changed my oil even though they changed it two weeks ago. They asked me to return in 1k miles to check oil level to see if some sort of leak is contributing to the problem.
- Filled my tank up with super.

All for the price of any oil filter.

Not sure about the motivation behind this last line item other than to keep me happy. The guy pretty much said that "these cars require frequent decarbonization if you use them for short trips."

I'm on the freeway my fair share but I don't use this car as my commuter (take the bus.) Even so, it eems odd that you can't use it as a city car w/o frequent service.