S6 which refuses to pull correctly

[HMS-S6]

Most of you on here have seen me rattle on endlessly about my S6 which refuses to pull correctly whatever i change (and believe me, its EVERYTHING!), but today i may have made a breakthrough.
I thought the knock sensors were retarding the timing, but after buying new (no difference) and then running the car with them both tied out the way (not a good idea i know) i finally ruled them out!

BUT.............If i start the car THEN with it running unplug the crank position sensor (which is also new!) the car pulls spot on - the fastest its ever been

I know the sensor is ok, but does anyone have a clue as to what it points to?

I am told that it uses a 'memory' position from cranking in order to run.

[prj]

Your car goes into limp mode most likely, and it does not read other sensors as well.
You will probably get a similar effect if you just unplug the MAF for example.

That doesn't mean the sensor is at fault.

[HMS-S6]

Your car goes into limp mode most likely, and it does not read other sensors as well.
You will probably get a similar effect if you just unplug the MAF for example.

That doesn't mean the sensor is at fault.

No. Limp mode is completely different, it limits the boost to 0.4 bar.

[driftin jo]

That's an odd one for sure , if the sensor wasn't working it wouldn't start , weird .
The only thing I can think of is that there is some sort of electrical interference going on when the engine is running , possibly in the wires from the sensor to the ecu . I would try running my own wires from the sensor to the ecu . I'm not an expert with electrical things but if no one else has any better ideas its probably worth a try.

[prj]

No. Limp mode is completely different, it limits the boost to 0.4 bar.

You are wrong.
0.4 bar limp mode means that the boost controller part is in limp mode.
If you disconnect the MAF, your fuel part will be in limp mode, which will by no means hamper boost meaning that will boost just fine with the MAF disconnected, but fuel and ignition will be in limp mode.

There are two limp modes in M2.3.2.

[HMS-S6]

You are wrong.
0.4 bar limp mode means that the boost controller part is in limp mode.
If you disconnect the MAF, your fuel part will be in limp mode, which will by no means hamper boost meaning that will boost just fine with the MAF disconnected, but fuel and ignition will be in limp mode.

There are two limp modes in M2.3.2.

I'm not wrong, with the MAF disconnected it also limits the boost - i have done this only today! As does the Camshaft sensor and knock sensors

What do you mean by M2.3.2.??

[HMS-S6]

That's an odd one for sure , if the sensor wasn't working it wouldn't start , weird .
The only thing I can think of is that there is some sort of electrical interference going on when the engine is running , possibly in the wires from the sensor to the ecu . I would try running my own wires from the sensor to the ecu . I'm not an expert with electrical things but if no one else has any better ideas its probably worth a try.

Thats the problem - i'm not electricaly minded realy either! I need to do a 'data log' to see what sensors are doing what but don't know who can do it with me.

[prj]

I'm not wrong, with the MAF disconnected it also limits the boost

It does not... last time I checked anyway.
I'll check again tomorrow

P.S. This does still not change the fact that there are two limp modes on Motronic 2.3.2. Also I am quite sure fuel part will go into limp mode with that sensor disconnected and boost will be fine.

[newsh]

This is interesting, does the "other" limp mode result in a partial reduction in boost and flat feeling to the power?

[prj]

Yes, car feels dead from 2000-4000 rpm. And comes alive after.
Turbo spools slower as well due to this... but boost goes over spring pressure.

[newsh]

I've had this with my car, after a WOT run through the gears boost would be reduced but only down to about 0.7Bar as opposed to 0.4Bar and yes engine feels really dead low down.

[Jamo]

I'm not wrong, with the MAF disconnected it also limits the boost - i have done this only today! As does the Camshaft sensor and knock sensors

What do you mean by M2.3.2.??

100% agree you get violent boost cut with the MAF unplug.

MAF plug came away when I was doing log run up MRC hill and it was vicous

[newsh]

I think you have to start the car with the maf disconnected to run without it.

[HMS-S6]

I think you have to start the car with the maf disconnected to run without it.

Any which way, what i am feeling is different, with the crank position sensor unplugged i get 0.8 bar on stock ecu and 1.4 on my mapped one and the car pulls like a train!!

[HMS-S6]

I've been told by everyone that the G40 camshaft sensor is only used for starting, but i have just read this http://forums.quattroworld.com/s4s6/msgs/22580.phtml which states that it is used fo knock reduction too!!!

I bought the car as a non runner from a guy who reported that it ran fine aside from that. When i bought it someone fitted an extremely cheap aftermarket Camshaft sensor (thought it was strange that it was 'on the shelf'), sugesting that the fault only started after this was fitted, is it possible that it was either not the right sensor or it was attached to the bracket in the wrong position?