mpurewal

My Q5:
- 2010 Q5 3.2 FSI, 34k, picked up in June 2009
- Maintained by Audi (Audi care)
- Fuel - 99% of the time Shell 91 octane
- Typically drive around the city plus some highway - in S mode at times

Issues:
- Rough idling/shudder about 2 months ago
- 2-3 tries before the car would start (usually twice a week). Over the last 3 weeks.
- Check engine light on for about a day (2 days ago)

So of course I came to the AudiWorld and other Audi forums (the Audi community is awesome ) which led me to believe this might be a carbon buildup problem based on the symptoms. I took it to my Audi dealer yesterday (Toronto area) and they confirmed that this is a carbon buildup problem. They'll be keeping my car for a few days and replacing the injectors under warranty - very decent dealer btw, always look into and fix any issues I bring to them - of course it helps that I'm always right

For those interested here's a summary of the information I've collected....

Issue - Direct injection engines such as FSI get carbon buildup on the valves and injectors because there is no fuel passing over them as it does for other engine designs - so no cleaning. This leads to misfires, loss of HP (substantial) and potentially other issues for the engine.

Turbo engines - 3.0 T (supercharged) and 2.0T seem to suffer a lot less from the carbon buildup issue, possibly due to higher engine temps in the manifold which burns off the carbon deposits.

What doesn't seem to work to prevent this:
- Catch cans don't have much effect (don't know the technical details are but something to do with the "gunk" coming out of the engine which isn't prevented by the catch can)
- Frequent oil changes
- Fuel additives (the additives never make it out to the valves so they have no effect)

What may work:
- Always using approved gas (top tier with detergents - not really convinced on what impact this would have...maybe burning cleaner so less deposits making it out to the valves)
- DIY cleaning agents for valves (probably shouldn't try this unless you know a lot about cars - I don't)
- Driving for a long distance (highway) once or twice a week - perhaps also combined with higher revs for a limited time 3000 - 40000rpms or so (to burn off deposits)
- Spirited driving (to burn off deposits)

Warranty and other stuff:
- Most decent dealers will clean/replace under warranty once there is a check engine light and error code confirms (there might not always be a check engine light). Might want to make sure the error code wasn't simply turned off.
- Audi doesn't seem to be doing anything in terms of adding this to maintenance probably due to the amount of time it takes; dealer told me half day's worth of effort. This is quite sad and unreasonable as we as customers who purchase these luxury products should be entitled to having these products work...seems basic to me.
- Out of warranty you're looking at about $500+ every 3 years or so. Audi should step up and extend the warranty for this issue, likely though they're probably waiting for a class action.
- For dealers who try to ignore you I suggest you tap into the great wealth of knowledge available in this forum and others so you can challenge your dealer. Persistence is also a great technique....

So that's it...if you have an FSI engine you will eventually get carbon buildup and possibly have to dish out some $$$. As for me I've ordered an S5 with a 4.2 V8 FSI (new S5 with 3.0T is just too ugly) which should be arriving this Christmas....maybe I can get a discount on the valve cleaning with two FSI engines I'm an optimist....seriously though I will be writing a letter to Audi NA....this is so not cool Audi, clean up your act.

ELEVENS

Excellent and accurate summary, nice job. My discussions with Audi was fruitless on this matter -my car was still under warranty coverage too with 30K miles - so I had to do it myself. It took over 13 hours of dirty, tedious, backbreaking labor. 30 horsepower was restored post-cleaning

You are absolutely correct, Audi needs to clean up it's act. Here's some carbon **** from my car (before/after):

UrbanExtant

It's unlikely Audi will do anything to fix the previous engine designs, but I know the new engine, the 1.8T, that they just designed with VW has port injection as well as direct injection. It seems they do learn, albeit slowly.

uberwgn

They have updated and improved the vapor separators over time:

uberwgn

I believe this is at the heart of the matter. During normal driving, these cars turn ultra-low revs rarely exceeding 2,000 rpm with around town driving.

Someone else appropriately said: A redline a day keeps the (Audi) doctor away

johncaravello

Thats my theory for all engines. They need to be worked hard on a regular basis.

ELEVENS

Port injection, combined with DFI, is effective at keeping the carbon monster away, Neither of the last two "solutions" are an effective fix. The RS4 has an uber-efficient triple-stage cyclonic vapor separator but crankcase vapor is only part of the problem. A study of the VW FSI patent reveals the carbon comes from 3 sources: Valve overlap ("internal EGR"), seeping valve oil seals, and crankcase ventilation vapors. Several reports of elaborate vapor catch cans in addition to the RS4's cyclonic system have shown to be useless. The patent lists a half dozen or so systems to deal with the known carbon buildup problem.

Here's a link to the patent. It's LOADED with useful information and a thorough study of it will get you a gold star!

http://www.google.com/patents?id=fLI...page&q&f=false

rs4-380

I've got a 3.2 q5 with 33k miles and a 4.2 s5 with 19k. I plan on opening then both up in the near future to check on the buildup status. It will be interesting to see if given their different normal usage which one is worse.

rs4-380

by the way, I hope they do a mechanical cleaning along with injector replacement or you aren't going to see much difference.

DrV

mpurewal,
You may want to read my thread about my experience with carbon buildup in the exhaust air ports.
https://www.audiworld.com/forums/sho....php?t=2816385