I took my car to the dealership with the yellow engine light on and was told that there is carbon buildup in the engine. The dealer (Audi of Brookline) said that they don't know why this happens, but it needs the engine to be stripped and cleaned. I see a thread on this topic, but confess that I don't really understand most of it.

Can anyone explain in non-petrolhead terms why this happens? Was, for example, my "fantastic discovery" of $1.79 93 octane petrol, not such a fantastic discovery?

Any enlightenment would be really appreciated.

Thanks
Marc

 

cant say specifically why YOUR car built up carbon, but prolly 80% of the time, its because the car is babied, and not driven hard enough.
i have heard of ferrari's doing the same thing...because the owners just drove them around like a cadillac...push the car harder, try a bottle of seafoam. that would be an odd thing to do to such a new car, but if you've got carbon buildup...id give it a try, it surely CANT hurt.

93 octane in central pa is between $1.80 and $2.00/gal so that doesnt sound like the problem...but i would stick to a name brand, such as sunoco, shell, exxon, etc...



ps
if yer afraid to blow the carbon out of your car, just bring it down to central pa, and i will gladly do it for you! no charge!

 

The heavy carbon build up is mainly due to the way an Audi recirculates exhaust for NOx control, by adjusting the cams for massive overlap. Lots of the exhaust goes back into the intake, to be recycled, cooling the combustion temps, reducing NOx. The side effect is carbon build up. It's particularly bad on FSI engines due to fuel not spraying on the valve and "washing" it. I seen the MIL thrown on the 3.2 FSI with less than 30,000 miles multiple times, and I've scraped chunks of carbon off valves on an RS4 with low miles.

The best way to prevent/minimize this, is to use Top Tier (and of course premium) gas. Once it's an issue have your local Audi dealer do an injection cleaning service (pressurized cleaner sprayed into the intake, and may throw an additive in the fuel tank and even run another cleaner directly into the fuel rail).

The vehicle does need to be driven hard at least once in a while, because these engines were designed to move a lot of air, but the fuel quality is going to be the main issue here. Driving the vehicle hard will clean out the combustion chamber real good, but does little for sucking off carbon already bonded in the intake track.

 

Thank you very much for the responses. The car has been fixed by Audi of Brookline and all seems well at the moment.

As for driving it hard, have you guys ever tried to drive fast in or around Boston? Firstly there is the issue of Boston drivers who haven't got a clue where they are or what they are doing, other than looking for the next Dunkin Donuts stop. If they are in the third lane of the highway and they see a DDs on the right, they throw a 90 degree turn across two lanes of traffic to get there. Given the fact that everyone else has their head up their *** too it amazes me there is not carnage on a Chernobyl-esque scale every day.

As soon as you leave the I-495 "safety ring" (inside which non Bostonians should not venture unless they are writing a comedy script) all roads, even minor ones in deepest darkest Maine, are infested with Staties, who in New England are the meanest, most miserable barstewards ever to don a badge.

I was ticketed twice in the middle of nowhere VT and nowheresville NH within the first month of owning the car, the second one resulting in a court appearance in Laconia, NH which was like stepping into a Jerry Springer show.

So.....I DO try not to baby my beauty, but I have suffered for my art.

Thanks again for the replies guys and happy motoring.

Marc

 

Scout out a section of road with alot of visibility and no traffic as a back up.

 

The list of RS4's having this problem keeps growing and most problems start before the car even has 10k miles. Most of the owners swear they put nothing but tier 1 fuel in the car, which is probably true. After numerous CEL's, my dealer cleaned my intake valves and the car finally ran great - for about 1000 miles, then they cleaned them again due to more CEL's and gunked up valves. The irony in the whole deal was that Audi tech and service advisor were asking what gas I used (Shell 93 exclusively) while the Service manager recommended a gas station down the street that doesn't even sell tier 1 fuel. I do give the manager credit because he's the one who decided to test the fuel system, which uncovered several bad injectors (they would not seal properly and could not hold pressure) which was the reason for the cold start misfires. So were the injectors damaged by running tier 1 fuel exclusively or all the carbon in the combustion chamber? I'd have to say the latter.

What do we know? FSI engines can have build-up problems. The RS4 4.2FSI has the same problems, but they tend to occur even faster. No grade of fuel cleans the intake valves and the additives in tier one fuel apparently can't keep the RS4 fuel system from falling prey to the issues caused by carbon build-up. I don't live in Boston so I can easily drive hard enough to get the engine over 7k many, many times to/from work. If a tech asks me if I drive the car hard, I reply with a glare. We're not talking about blowing the soot out of a motorcycle exhaust here. The fact is, the carbon build-up seen in RS4's is so serious that fuel quality and driving habits really don't have much of a beneficial effect. If you've had your RS4 intake valves cleaned once, it probably won't be the last time.

 

Seems like these cars have serious issues from DRC shocks to engine carbon buildup? What else? More importantly, what could go wrong where I would have no choice but to go to the dealer for the work?

 

My friend doesn't drive an Audi, but his car had some carbon build up. A friend of his told him to use about two BG 44K bottles... one for every other fill up for the next 4 fill ups of gas. His friend swears this stuff works and after looking up some reviews online, it looks legit.

Does anyone think Restore Engine Cleaner every 6 months might be helpful as well?

It's probably worth the money and you won't even have to leave your car at the dealership!

 

Hi Guys:
I was intrigued by the comment on bad injectors causing cold weather misfire. Does anyone know if this is an electronic (read the computer) or a physical test? I have the same issues and since Audi programmed out the misfire "check engine" light, no fault codes show up.