erionracing

2010 s5 74k. Well engine light started blinking. Took it to Audi and suggested the carbon flush by BG, did it and a month later engine light blinking again. This time i knew what was wrong. On the gas it started to shutter almost misfiring. So i figured it had to be the injectors possibly clogged cause i had just replaced the coilpacks and spark plugs myself. Dealer stated yup and that it was under warranty due to the fact BG did the carbon flush. so they replced the injectors and found a ton of carbon on the back of the intake valves. Some of the valves had almost 5 mm of carbon built up.
So there was so much carbon built up it was everywhere. The normal cost to clean out this issue is just around 1k here in Md. The carbon flush is about 199 bucks, but that does clean the valves just the injectors. So Cleaning the valves will cost me 600 bucks!
Direct injection vehicles will all have to be cleaned around 50,000-70,000 miles.

snagitseven

Just curious, have you been using Top Tier fuel over the car's life?

erionracing

Yes only top tier fuel 94 octane. The audi mechanic stated it really doesnt matter there will always be carbon built up no matter what octane u use or race fuel. Carbon is always left over from a burn.

snagitseven

I would have to disagree that all FSI engines will require carbon cleaning as soon as 50K-70K miles. There have only been a few I've seen in the various AW forums where the check engine light came on or was flashing as a result of carbon build up. Not to say it doesn't happen, as it obviously has with your car, but if it was universal, the forums would be flooded with people reporting the issue.

Audi has addressed carbon build up the secondary air ports of 3.0 and 3.2 FSI engines, where fire from ignition can't reach them lower in the cylinders, by supplying a 10 yr/120K mile extended warranty if it causes a CEL.

Your experience notwithstanding, I would also disagree with your mechanic that Top Tier fuel doesn't matter. Read the recent independent study performed by AAA that clearly shows it does make a difference in helping reduce carbon and even in many cases, can remove existing carbon deposits.
http://www.aaa.com/AAA/common/AAR/fi...ull-Report.pdf

erionracing

All direct fuel injection vehicles build up carbon...every single one. and whoever tells you it doesnt is absolutely wrong. Ive been in the industry for 25 yrs and your right i dont see a lot of these issues because audi takes care of it at service under service increments.
In the service manual of every audi s5 2010 and up. I spoke at length with the mechanic and advisor, both stated its a problem and will continue to be a problem until its addressed. Both stated the fuel injection flush will help with cleaning the injectors so they will not clog up and its on the 55k service. Which i had done.
carbon builds up in all direct injection vehicles. there is no way as of today to stop it. Ive opened up only 2 audi intake manifolds and found the carbon build up. So from just these two engines ive seen... i believe it to be true.

snagitseven

I don't disagree there will be some carbon deposits accumulated - it's the nature of the beast. But again, if severe carbon build up notably affecting performance on all FSI engines, requiring an extensive cleaning and not just a fuel flush, we would be seeing an Audi owner uprising along with multiple class action suits.

SloopJohnB@mac.com

And yet, it occurs frequently enough that special tools are used to walnut shell blast and vacuum individual ports.

Here's one for BMW (another direct injection child).

BMW Walnut Media Blaster | Bavarian Autosport BMW Parts and Accessories

And yet EPA doesn't consider it a violation of emissions statutes probably because the cat cleans up exhaust and the driver is simply stuck with poor performance.

BTW....TT fuel won't clean intake valves on DI engines.

erionracing

yes they had some device that cleaned it pretty thoroughly, i believe it was that. I had cleaned it with a light pad and used csi gas canister which is very light spray and it took maybe 20 mins to soak and clean, but it came straight off. just a hassle to take the manifold off. all in all it took about 1.5 hrs to clean thoroughly and put back together. Next time i do one i'll post pics of how much carbon builds up on the back of the valves.

snagitseven

I'm curious..is there a significant difference between port injection and direct injection designs re the intake valves gathering deposits?

JD15

Yes, carbon build-up is far worse on DI than port injection because fuel is never in contact with the intake valves with DI. Lexus has a ubiquitous 3.5L DI V6 with both port and direct injection that mostly eliminates carbon build-up and Audi also equips some vehicles with dual-injection, such as the S3 in Europe, but chooses to reduce cost for the NA market and let American owners pay to clean intake carbon on their own dime.