dripppps

I just hit 50k on my beautiful A8. Ive gone through all of the 55k service procedures, but I typically do a cleaning of the fuel system around this mileage.

Can any recommend a good fuel system cleaner for the D3 A8? Anyone use Seafoam treatment on these cars? Other recommendations?

snapdragon

A waste of time, it doesn't have a carburetter.

mishar

Seafoam can be a good way to kill your MAF sensor. Besides that, why would you do it? It is way too early for any carbon deposits.

The only thing I can recommend is injector cleaner from time to time. Good gas already have that additive but some more is good too. Makes engine smoother and gas millage better, but don't expect miracles.

uberwgn

Here's the VAG product:



About $6 from the VW dealer, about $10 from the Audi dealer. The A8 may need 2 cans, refer to label.

MP4.2+6.0

Notice from the OP post it is a 2007. Thus it's FSI. Therefore, your suggestion about an fuel system type cleaner (like a Techron) is of very limited utility except basically for the injectors themselves, since the fuel of course doesn't go thru the port to wash the intake valves, but instead directly into the cylinder.

Owning a Mini S with the direct injection turbo 4, problems with intake fouling are well known on that motor. Ditto on the Audi 3.2 FSI, with some reports here and there on the FSI fours, once in a while on the (always FSI) 5.2 (as in, S8 and presumably S6) and much more sparing on the later FSI 4.2s. Unlike the Audi world though, In the Mini world they seem pretty accepting of Seafoam as the quasi standard approach--that plus catch cans basically.

From having seen it already once on the Mini, the motor fairly quickly can get noisy and idle unevenly (like within a week, not over months or years, so the issue is pretty pronounced and comes on pretty fast). Sure enough, IF you can get the Seafoam to actually come out of the can (surprisingly difficult from my experience), you just run it in well past the MAF by running the spray tube under one of the clamped rubber joints in the intake system close in to the cylinder head and definitely post-MAF. Then motor chugs and wheezes some as you get it in, and net, sure enough at least on the Mini the bad idle stuff and the intake noise presumably associated with the fouling im mediately goes away. It's been a year + since I had to do it (once so far), and all good so far.

Fully agreed with you on Techron with a port injected 4.2 (thru 2006) or any W12 like mine, but the FSI situation is different here, and unfortunately most all the big manufacturers seem to have stumbled some on the first gen FSI designs as far as the crud that comes in from the PCV system. Even worse, some motors (like the 3.2 apparently) also have air injection ports on the exhaust side that are also clogging up. Mini (BMW) has already done one redesign quietly, and the Audi 3.2 seems headed for oblivion. But a huge nightmare if you really can't even get to the valve area in any easy way if you have to do a more aggressive clean.

dvs_dave

Agree, the gasoline direct injection inlet coking issue is a major cockup on all fronts. Although why don't diesels suffer in the same way? They've had DI for 20+ years now.

mishar

Diesels have direct injection from the day one. They don't create high vacuum in the intake manifold, so they suck way less oil around valve stubs. I am not sure about oil vapors, but oil is what is creating those deposits.

Injector cleaning is exactly what I am talking about and carbon deposits on an A8 has still to be proven. As a picture speaks thousand words:

MP4.2+6.0

we probably aren't going to see a lot of data or consistent reports from the 2007-2010 A8's. Thinly sold car, especially in the later years as the annual sales just kept going down with all of the 2007 S8 intro, the 2008 economic crash and the end of life cycle. Probably most of the data to be found will come places the motor crosses over--higher volume S4s and S5s while it was 4.2; lost track of the 4.2 particulars on the Q7 but a lot were sold as 3.6's. I'll exclude the higher strung R8s and RS4's given different tune states, plus again fairly low total volume.

s4master1

have you seen the intake manifold and variable nozzle turbo lately on a tdi lately?
they do have carbon build up.

s4master1

carbon deposits on an A8 has still to be proven.

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2 A8s in the shop today for cleaning plus 1 A3 2.0
all 3 cars look the same in the intake valves.