tingyunliu

Hi, I know little about cars and am seeking for advices here...

I bought a 2012 S4 2 years ago (2011 July). Now the car has about 38K mileage on it. Last week, the check engine light went off, and I sent it to the dealer Thursday. Today is the third day and I am still on the loan car. The service manager told me at the end of the first day that the engine misfired and had carbon buildup. He told me that they put some additives in the engine (to remove the carbon?), and the light is no longer there. However, they needed to keep the car driving more miles to make sure the issue is resolved.

My questions are

1. What is the root cause? Is this the right fix?
2. What should I request, if any, to the dealer?

FYI: I have Audi care, therefore, all services on time at dealers. I always use 91 gas from 76/Shell/Chevron.

Any advices are more than welcome.

Thanks,
Ting

safetywork

Ting, I'm not sure if my comments will help. My only experience with carbon build up were on 993 Porsches and that was due to an inherent design flaw (at least thats how I understand it). I've heard that every once in a while, it wise to drive with the vehicle in gear towards the upper rpm ranges but this could be a myth. I'm not sure if the reason why I never got one of these warnings is due to the fact that I track my cars. ???

Good luck, please keep us posted.

Tweakophyte

That stinks.

What is your typical driving style? Do you wind the engine out or short-shift? What does your daily commute look like?

These cars are supposed to be pretty good with the carbon.

TO407S4

Stupid question... what gas do you use?

helix139

These cars don't really get carbon buildup on the intake valves like the 4.2FSI. A few have gotten it in the secondary air intake system, which doesn't cause power loss but will cause a CEL. At that point, your two choices are to either have aftermarket software code out the SAI readiness check (none of the tuners do this yet IIRC) or have a cleaning performed. NWS4Guy had to have this done on his car and it involved a high pressure water jet and dropping the engine I believe.

brooklyn86

You should contact him directly, but I believe it was covered under warranty, FYI.

tingyunliu

Hi All,

Thank you all for all the replies. Here are some more info amd answers for you.

1. I always use 91 gas from chevron/Shell/76 (in sequence of frequencies)
2. My commute is 80 miles/day. I drove the first 35K in 1.5 year, then I only drove it during the weekend for 6 months. I restarted to use it for commute two weeks ago, and this thing happened.
3. My driving style: I am slightly more aggressive compared to average drivers on the road. I am sure that I must be a mild driver in this forum.
4. The dealer told me that the car would be ready today, the 4th day. He told me that it's common and it's due to engine temp too high??? He said they always recommend to add some kind of "additive" to the gas every 3K to keep engine clean (?).
5. He told me they just put "additive" in the car, and kept driving the car to make sure the light would not come back.

What I worry the most is if they really fix the problem, or they just hide the issue as the warrantee is going to the end soon. I appreciate if you have any inputs.

Regards,
Ting

NWS4Guy

I'm inclined to think this might be carbon buildup in the secondary air system, not the intake valves. I have had to get mine cleaned out (under warranty) already, and your fuel and driving style don't lend to carbon on the intake valves. I'd ask for some specifics from a tech at the dealership, not a service desk person. If it's Secondary Air system (you can also pull the check engine codes using Vag-Com cable and VCDS software, it will explicitly state Secondary Air system), only pulling the top of the engine apart and blasting the secondary air channels out will clear the obstructions and Check Engine.

tingyunliu

Thanks a lot, NWS4Guy. Your explanation is very clear, and I will ask the tech about the real issue if possible. Will update.

tingyunliu

The dealer called and told me the car is ready for pickup after 4 days. He confirmed that the buildup was on intake valves (and caused misfire).

Let me try my best to describe what he told about how they cleaned it. Please forgive my poor knowledge and vocabulary.

1. Open up the manifold.
2. Put some solutions into the intake valves (?)
3. Let the solution stay there for a couple hours to "resolve" the carbon buildup (?)
4. Suck out the solution.

That's the idea I got although I don't really understand it.

Any comments?

Thanks,
Ting