[Biturbos4] Fuel System Service (was: Fuel filter)

Keman keman at interwolf.net
Sun Jan 4 23:02:00 EST 2004

Fuel filter? Not really .. it's pretty much a lifetime filter. No suggested
change interval that I'm aware of.

If you want to service the fuel system find someone who has a pressurized
regulated canister designed for fuel injection cleaning or bring it to the
dealership to be "decarbonized".

To do it yourself, pinch the return line, hook up the canister to the feed
line set at around 60 psi. We use a special decarbonizing cleaning product-- 
you can buy it at any audi dealership for about $10. You just idle it at
1400 rpm until the can runs empty. Pull the fuel pump relay first. Be
prepared for the most noxious smoke coming out the tailpipe you have ever
smelled. It will make your eyes water... so do it outside. Then get it all
hooked back up when the engine dies.

Here is the important part: change the oil, filter, and -spark plugs-
immediately afterwards.

This stuff is nasty, real nasty. It gets past the rings and thins out the
oil. You must get rid of it. It also ruins your spark plugs, they're totally
gunked up with carbon and other delightful things after just 15 minutes.
S4's take double platinums and they are expensive. It's a hotter plug than a
normal 2.8, surprisingly.

After that, take it out and keep it above 4000 rpm... every chance you have
at giving it WOT, do so. Drive it around like this for about 3 miles.

You'll notice a smoother idle after this is all done, and audi pays for it
to be done under warranty any time a customer complains about a poor idle or
loss of power. The injectors get a major cleaning and carbon on the valves
is burned away as well as a good amount on the pistons. You would be amazed
at how much builds up on our engines so quickly! The biturbo is a rich
running engine...

I got 30 millibars of vacuum gained back afterwards ... it was 550 at idle
when brand new, then dropped down to 480 with 78k miles ... after this was
done I'm back at 510. This is a good thing...

I've personally seen engines run a hell of a lot better after this was done,
and I swear by it. This is not some additive you put in the gas tank, you
run the engine directly off of it and it doesn't produce a lot of power so
it takes about 1/4 throttle to get 1400 rpm. It is safe for catalytic
convertors and O2 sensors, but boy does it get them hot.

Good luck!

- Keman

Brad R wrote:
>> One other question for now...I just took my car in for the maintence
>> service.  When looking through the manual, I didn't find any
>> specified interval for changing the fuel filter.  Is there a
>> suggested interval for changing it that I missed?
>> Thanks,
>> Brad
>> 2000 S4 - 6speed

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