Fuel filter replacement

[Enne&Effe]

Hello everyone, I try to change the fuel filter of my RS4 but I wasn't able to remove it. Can you explain me te procedure to replace it? Is it necessary to remove te rear seats?
Thanks in advance.

P.S. My car had a little hesitation at WOT at 5.000 rpm. Sometimes I had "Charge pressure positive deviation, fuel trim bank 1&2 (Add) too lean)". The problem seems to be solved: I changed the boost pressure sender for about (on the top of inlet mainfold) 90 Euro ?!? I also rotate the upper screw of the N75 for about less than 1/16 of turn clockwise.
By the way I've changed also oil filter, air filter and the 6 sparks: It takes a lot of time...I had to dismantle the air box and the water tank!!!. Another question: there is a NON connected hose below the water tank. Is it correct? I Replaced also the motor oil: I used the Valvoline VR1 10-60. What do you think?

[Golich]

Yeah the fuel filter looks quite akward to replace. I looked at doing it earlier this year when mine started leaking. But I was recovering from a broken arm and it looked a real pain. The dealer did it for something like an hours work. Audiworld has a technical article on it. You don't have to remove the seats. I pretty sure you don't have to drain the tank either. But the volume of the fuel filter will pour out.

The unconnected hose you refer to should not be connected to anything. Its the blow off hose. Make sure its routed such that hot steam can't blow onto anything sensitive. e.g. electrical!

Your fuel trim DTC - I would have thought that was more related to a MAF than the N75 valve. But as you say it seems to have cured the problem. Keep an eye on it.

Not sure about the oil. I stick to what is recommended. The RS4 has some oil condition monitoring for the variable servicing not that that should stop you. But I'm on that.

[dodgydave]

Changing the filter took me 30 minutes with this guide: http://www.audiworld.com/tech/eng.html

[don]

Just while where on the topic of servicing filters... this guide for servicing the air filter looks helpful aswell. It is for the S4 but looks the same as the RS4 to me.

http://www.audiworld.com/tech/eng17.shtml

If you've looked under the bonnet at it, the piping and wires hanging off it might make you think twice. It's still a bit of a job though but not such a puzzle with this guide.

I also serviced my air filter for the cabin air the other day aswell and vaccummed it out, quite a bit of grit builds up. It sits passenger side (UK) behind the battery under the windscreen, cover clips out laterally if you pull it towards the front of the car.

[tartan_rob]

Doing this:"I also rotate the upper screw of the N75 for about less than 1/16 of turn clockwise. "

causes: Charge pressure positive deviation - I think. Turning the screw clockwise up the boost a touch, turning anitclockwise drops the boost a bit. Check for leask though as well could have been the MAP sensor.

[Enne&Effe]

If the solenoid lift the N75 piston against the spring force, when you turn clockwise the screw you should increase the spring force so the mechanical boost control pressure decreases but the ECU increases the duty cicle.
Is it correct?

[Enne&Effe]

If the solenoid lift the N75 piston against the spring force, when you turn clockwise the screw you should increase the spring force so the mechanical boost control pressure decreases but the ECU increases the duty cicle.
Is it correct?

[dodgydave]

Clockwise will decrease boost pressure and anticlockwise increase it a bit. The plunger lifts to blow off boost pressure into the atmostphere to delay the mechanical wategate response. This means less spring pressure = more boost pressure!!
BUT I found out if you screw it a bit to far either way it actually stops working. I just yesterday played a lot with it and it is very difficult to get the desired results. A lot of start-stop-bonnet-up-screw a tiny bit and so on ...... serious, I spend 2 hours yesterday night like this.

[Enne&Effe]

BUT I found out if you screw it a bit to far either way it actually stops working.

Fortunately the N75 is still working: my brother and I reached 250 Km/h with no problem at all.
The most important point is the fact that the little hesitation disappeared. I think the problem was caused by the sparks (I have some doubt) or by the boost pressure sender that was covered by the engine oil (probably by the oil steam) or by the N75 that I have adjusted (this valve was changed this summer so it's new)