gk1

I had a few DTCs the other day related to multiple random misfires. Since I know this seems to be common when cold I cleared it with VCDS but it came back two more times. On the third MIL I took it to the dealer. They have performed software update TSB 2020645/3. I have not seen that one posted before or on any of the TSB links. I will check Bentley tonight to see if they have any information on it.

The service manager stated if this update does not solve the problem then the valves may need to be cleaned. (Crosses fingers) FYI I've use "top-tier" Shell V-power since new so gas quality should not be their scapegoat. Currently at 18k miles.

The G Man

I had the same issue since my 08 A6 was new, had the valve clean once and been using the VW fuel additive which seems to work pretty good. I had the same software upgrade as you, I assume thats the TSB the dealer did on your car. It seems to misfire less on cold start now since the TSB was done.

gk1

Agreed the car does seem to high idle smoother now at cold start.

gk1

I looked in the Bentley and the May 2009 TSB 2020645/1 indicates to use the Audi Fuel Additive (G 001 700 03) and that the production solution is "Software update in development". I assume that is the TSB 2020645/3 they performed.

oaktreelimb

You need to get Valve cleaning performed. This is not a problem with bad gas. The fuel injection system in the 3.2L engine in the C6 is direct injection so the back of all intake valves never got fuel flow by to clean it. Over time it will accumulate lot of deposit on the back of the valve and cause cold start misfire. The severe one will cause lack of power, stumble.
The best way is to remove intake manifold to see the valves and clean them. You can do it yourself but you may not have tool to replace injector seals.

gk1

I've read the other posts where the valves underwent manual cleaning, but I also see the posts where this did not alleviate the problem entirely or it simply returned. I've been around long enough to fully understand the functioning of the fuel injection system in the 3.2 FSI. I know the fuel does not wash past the backs of the intake valves. A better question might be, "then what is depositing on the back of the valves?" Some speculate that not driving hard enough may lead to the sort of issue that requires the manual cleaning? (I don't know). Audi even claims that not using "top-tier" fuel can cause these types of issues. In my post I'm pointing out that I have always used "top-tier" fuel and Audi approved engine oils so those two items cannot be used as their explanation for the problem. I also do not drive "mildly". Having to perform a manual valve cleaning every 18k miles is a completely unacceptable answer by all accounts.

So far the SW update is working, the MIL has not returned and the car does seem to cold start better.

gk1

Before and after TSB 2020645/3

aka "Control Module Part Number" + "Version" in VCDS.

OLD
4F2 910 559 D 0060

NEW
4F2 910 559 H 0020

2008A6

gk1 - I also had this TSB (2020645/3) done last week. Did you ever figure out what the TSB does to the ECU exactly? I also have the same question as you, if nothing ever touches the back of the valves, what is it that causes buildup if it's not fuel residue?

gk1

No, I never found any more detail about the TSB. I think it is too new to show on the Bentley updates. Doesn't really matter the CEL came back on anyway. I just ran the Audi fuel additive through and I'm dropping it off at the dealer tonight so they can monitor it on cold start in the AM. Depending what they see will determine if they will perform the valve cleaning.

When I prompted how a car with just 18k miles could have a carbon buildup problem on the intake valves when no fuel washes past them I was only told "it just happens". However, when I asked what happens when this happens again in an other 18k miles he said it's not likely to happen again...a bit contradictory to not know why something is occurring but claim it is not likely to happen again.

mystrodo

gk1

I'm sure you read Audi_bug's extensive post on the carbon issue. if not..check it out. Every 18K does not seem right..something is wrong and I'd be very tempted to contact Germany motor engineering mainly because I'm not finding the "carbon" issue posts in the German and UK forums... granted most are running the 3.0 TDI but there's 3.2 owners also *but they use different brands of oil then we do.
Is it possible the crankcase oil itself could be causing this buildup..seems most dealerships are using Castrol in the US? I'm really starting to have thoughts about this.