<center><img src="http://pictureposter.audiworld.com/102074/second_and_fourth_gear_pulls.jpg"></center><p>Trying to think out of the box as I have tried everything obvious. I can use some help.

Since chipping my ATW auto trans A4 w/stock K03, I have been getting negative deviation as requested is less than specified charge. This is throwing me into limp mode.

As of this morning I have cured all other DTCs (secondary O2 sensor &amp; KS1) but am still getting the negative deviation code when driving hard in second and third gear.

I have also recently replaced MAF, DV, N75C, SJP, and primary O2. I have bypassed N249 and DV is connected to intake manifold. I have pressure tested intake side twice and very thoroughly pressure tested vac system (every individual check valve tested, etc) and now show no leaks (SJP had small leak). My fuel trims indicate no leaks.

I have always seen this in second and third gear, so today I decided to log group 115 (and MAF) in 4th from 2k RPM to WOT. Oddly enough no limp and actual versus specified curve looks ideal. I logged another 2nd gear run and BAM into limp mode again very quickly.

There are a few differences which may mean something (or may mean nothing):
- in 2nd gear MAF drops sharply; in 4th it ramps linearly.
- in 2nd gear engine load hits 175%; in 4th it doesn't break 150%.

Could my TIP be collapsing? I've heard that this can happen on K04'ed cars not on K03s. But the MAF dropping (admittedly after boost refuses to hold) makes me wonder if the sharp increase in negative pressure in the TIP in 2nd gear (relative to the more gradual increase in 4th) could be causing the TIP to collapse.

How is engine load calculated by the ECU and used. The drop in actual charge seems to occur right after engine load hits 175%. Is there some safety mechanism in the ECU that would be shutting things down when load hits a threshold?

Any thoughts on where to look next? It seems odd that in 4th gear higher actual charge is attained and maintained (2250+ maintained for 1k RPM) while in 2nd gear max actual charge is 2230.

 

Wrap the TIP in duct tape - are you serious?

 

Found some dated info at:
http://yarchive.net/car/engine_control.html
Don't know what ECU it applies to.

The second is the High Engine Load
Shutoff that protects the engine from prolonged load. It is triggered when the MAP pressure is above the protective setpoint for a programmed
number of seconds. Either protective trip causes the fuel injector pulse to be set to zero, shutting off fuel until the trip condition is cleared.

Where can I log injector pulse (in VAG COM) or otherwise determine if something like this is happening?

Or am I following the wrong lead?

 

What N75 are you running?

 

replaced original N75C (which was malfunctioning) with new N75C 1 month ago

 

<center><img src="http://pictureposter.audiworld.com/102074/third_gear_pull.jpg"></center><p>Re-charted original 3rd gear pull and actual charge starts dropping to limp when engine load = 175%

Is this a cooincidence or is there some type of shutoff.

If there is a shutoff, it's not the N75 because the N75 duty cycle looks good when boost is dropping. It's not the N249 as I have bypassed that and DV is controlled by mani vac.

Could it be fuel related? Injector pulse timing? etc? How else would ECU drop charge pressure?

Maybe this GIAC program (ATW/K03) is too aggressive. Anyone else running it?

 

The F valve also works well. I would say check for boost leaks.

 

What makes you think that a leak is the culprit?

I have pressure tested intake side twice. No leaks.

I have pressure tested every vac system component individually and as a system. No leaks.

My fuel trims indicate no leaks.

Plus my 4th gear pull holds more pressure than my 2nd &amp; 3rd.

No leaks!!

 

Running out of usefull suggestions here.....Maybe try getting ahold of an F valve and trying that out?

 

yup. wrapped the whole thing in zip ties. it was collapsing under extreme airflow.