alpinab7

I have had my 91 200TQ 20v for a few months. Last month during hard acceleration I "hit a wall"--felt like ecu fuel cutout. Bang--like someone killed the ignition just for a second. It happened twice. I filled the tank and it went away. I thought it was bad gas. Then it did it again once more.

Got a QLCC chip, 2.5 bar pressure transducer and a 2.5 spring. I assumed the problem was done. Now it does it all the time. It is exactly like before only more often so i am assuming it is not the chips but rather that the extra boost in excacerbating the problem. I got a 2224 code (overboost but could be from a long time ago?). Cleared it and even though the problem still exists (all the time) now I just get a 2231 code ( i assume the fault codes are blinked out in sucession even though I just get the same one over and over)2231 is:

From IA:
Idle speed regulation
Idle Air Control valve (N 71) binds when closed
Mass Air Flow Sensor (G 70) offset
Resistance at terminal connector of (N 71)
Idle Air Control valve (N 71) binds when open
Air leak between Mass Air Flow Sensor (G 70) and Idle Air Control valve (N 71)

I did the output test and everything "clicks" OK
I have checked the following:

Throttle position switch: resistance for open/close and graduated resistance ok

Pressurized the intake from after the MAF no leaks but a little air comes out of oil cap

Pulled the MAF out: coated with ****, air filter really, really, really dirty. Cleaned MAF, R&R filter.

Pulled fuel filter and blew trhough it. Very little resistance. Fuel goes through.

Pessurized top WG port. Holds pressure and vacuum.

Pulled the ISV which opens and closes with the output test. I can blow air through it when closed. I got a used one and can do it with that too. (not installed yet)

So I took out the 2.5 spring and put back the stock (big difference) it still does it but not nearly as bad.

Two other things I noticed. Driving home tonight: Floor it, boosts to 1.1 (really 1.4 because of the 2.5bar transducer) and it just holds there for a sec or 2. Then takes off boost rising and then bang. Cut out.

It does this randomly as far as boost levels go...cuts out below 1 bar or at 1.7. Usually does it at medium to full throttle.This morning it stuttered at .5bar (again remember the 2.5bar transducer changes the boost gauge reading)

I feel like this is definately an ECU induced fuel cutout. I had a problem which felt similar due to a bad AFM in my ALpina (which was not fuel cut out but worn carbon strips for the potentiometer in the AFM). It doesn't feel like a fuel pump/filter/pressure issue. It feels like a sensor problem or false air induced sensor problem.

I am still working my way through stuff but any ideas? I love this 220k mile beater and although I can afford it I don't want a new car. I had an M5 and still own an Alpina B7 but this Audi is perfect. Fast, comfortable, and I never worry about scratches or dings. Any suggestions welcome and thanks in advance.

CARSNPLANES

Can you "un-chip" it for troubleshooting? Or try another ECU with the old spring and the new one?
You are right , it sounds like an ECU triggered cutout.

4Driver4

The buck you feel is when the ECU kills fuel because boost has gone too high. Most likely situation is a small boost leak. Pressure test the intake track; I bet you have a hole in the michelin man hose.

alpinab7

seems to be a little air coming out of the oil cap. And that is just a slight hiss.

CARSNPLANES

Wouldn't you "lose " boost if there were leaks in the boost track? Then you wouldn't be exceeding it.
A leak in the boost track would give you a power loss, really due to an over rich condition, not an ECU triggered cutout, because all the air that is metering fuel, is not going to the intake,but rather out the leaks in the MM hose or intercooler etc.

boxerfan

Sounds like the over boost cut out to me so if the WG isn't leaking then the xducer must be on the fritz. Try an R mod or ground the FP relay and see if it goes away.