S2 ABY loses power over 4000rpm

[Alticity]

Hey!
I have a very annoying problem with my Audi S2 Avant ABY -93 the engine is original without MTM 303 chip

It lose power over 4000rpm, just like a fuel cut. The fuel pump is a Bosch 044.
The pressure do not drop when i hit 4000rpm, and its not like a ignition cut.

And its not happens all the time, maybe its random but i think its worse when its hot wheater like 20C++.

Anyone how know what it can be?

The last year i have changed alot of stuff without it have been better:

-New coils from 034 Motorsport
-New plugs
-New map sensor
-Checked for leaks

[Rikki Kitto]

Is it quite violent like you gonna go through the windscreen

[Alticity]

No, its just loses power.. The rpm goes fast up to 4000rpm, but after it goes real slow. If you understand?

[Rikki Kitto]

Mmmm no boost, sure you will get help on here soon. Sorry I can't help

[Alticity]

Okey! I was thinking about the MAF sensor or the fuel pump filter, any suggestions?

[UrS4boy]

No, its just loses power.. The rpm goes fast up to 4000rpm, but after it goes real slow. If you understand?

You've got threr or four main candidates:

1. Clogged catalytic converters, if still fitted.
2. Weak fuel pump, can't supply the required flow
3. Ignition problem, coils, plugs or coil to plug boots.
4. Boost leak, i.e. split hose that is normally closed at lower boost pressures but opens up at higher boost pressures.

On the last one, read the info at this link:

http://www.s2forum.com/forum/showthread.php?t=63974&highlight=boost+leak+testing

[Alticity]

Okey!
The car has been a project car from 2008-2011 so alot of parts have been changed.

1. the Catalysators are RS2, pretty new (2010)
2. the fuel pump is Bosch 044, pretty new (2010) The pump make alot of noise but people say its normal on the 044 pump? I do not know the condition of the fuel filter..
3. New Coils from 034 motorsport, new plugs without any changes. (changed 2013 after the problem came)
4. Have pressure tested from air intake to the intake manifold without any leaks.

The problem is not there all the time, yesterday it worked real fine. This make me think the problem is electrical? Typical come and go problem?

[macspring]

If your don't know the age of the fuel filter, i would change it. It is an awkward job, but it should still be done.

Most likely not the issue that is causing the loss of power, but the car needs a fresh fuel filter anyway.

044 pumps are noisier than the oem pump, in that they can be heard, but one gets used to it. I normally only sometimes notice mine with the window open at slow speeds, or if I out of the car and the engine is still running.

Best wishes.

[UrS4boy]

4. Have pressure tested from air intake to the intake manifold without any leaks.
The problem is not there all the time, yesterday it worked real fine. This make me think the problem is electrical? Typical come and go problem?

What pressure did you use to test for boost leaks? Needs to be at least 1 Bar (but not 2 Bar).

You could try the MAF connector. They seem to get dirty or pins get out of position.

G70 MAF info:

http://forums.quattroworld.com/s4s6/msgs/20442.phtml

Also general missing and hesitation testing:

http://forums.quattroworld.com/s4s6/msgs/22611.phtml

[Alticity]

What pressure did you use to test for boost leaks? Needs to be at least 1 Bar (but not 2 Bar).

You could try the MAF connector. They seem to get dirty or pins get out of position.

G70 MAF info:

http://forums.quattroworld.com/s4s6/msgs/20442.phtml

Also general missing and hesitation testing:
http://forums.quattroworld.com/s4s6/msgs/22611.phtml

I tested for ca 1,2bar without any leaks.

Thank you!

First im going to change the fuelfilter and clean the MAF sensor.
If i disconnect the MAF sensor when idling how should the car behave then?

[quattrostyle]

I'd say check your MAF connector as suggested above, it can lead to a varity of issues.

[220bhp]

I chased this same problem for ages when I first got my s2. Changed and checked just about everything. Then I changed one of the knock sensors because the wire was looking shabby, and the car was transformed.

[Alticity]

I chased this same problem for ages when I first got my s2. Changed and checked just about everything. Then I changed one of the knock sensors because the wire was looking shabby, and the car was transformed.

Nice! Is it two of them? And where is it placed?

[220bhp]

There are two on the side of the block under the inlet. One towards the front quarter of the block and one on the back quarter. a single bolt attaches each one to the block ,which has to be torqued up, not very much, and I cannot remember how much. It is very important to do it right so you will have to do a search on here to find out, it is something like 10nm. The other end is a connector on the bulkhead where the other sensors are.

[Alticity]

There are two on the side of the block under the inlet. One towards the front quarter of the block and one on the back quarter. a single bolt attaches each one to the block ,which has to be torqued up, not very much, and I cannot remember how much. It is very important to do it right so you will have to do a search on here to find out, it is something like 10nm. The other end is a connector on the bulkhead where the other sensors are.

I found it! One are blue and one are green, anyone have the parts number?
Torque is 20 Nm (15 lb-ft)

The car is going to a garage next monday to change the fuel filter, so im thinking about to change the knock sensors in the same time.

I am away from the car until friday, but my girlfriend took some pictures of the knock sensor connectors So i havent checked t MAF connector yet.