High rpm injection timing retardation?

[shizzler]

Just wondering if anyone has any insight to a strange problem my TDI developed today. Had been running perfect for about as long as I can remember, until just this afternoon. I usually do a wide open throttle pull on my highway onramps during my commute so I can definitely say its been performing great even as of very lately. However snow and ice on the roads have kept me from running wide open a bit less often though.

Today however when I go WOT, the engine pulls normally at lower rpm and hits a wall around 3000-3500 rpms where the acceleration dies. Boost is normal (17 psi), not spiking too bad (nothing over 20 psi). However the injection timing is falling wayy off. Basically reverting back to around 0 deg. I even saw a 5 degrees after TDC reading at one point around 4k WOT in 4th gear. As one would expect, a nice cloud of smoke and EGTs not too happy about it. No CEL or code.

Checked the most obvious thing by unplugging the MAF sensor. Exact same performance!
So I was wondering if anyone knows of anything obvious that could crop up all of a sudden, that would cause the upper rpm injection timing to retard so much? Could not find anything like this in a quick forum search.

Thanks for any help. I now have a vag-com, so tomorrow I plan to take some logs Anyone know which channel(s) I need to log for requested vs actual injection timing?

Many thanks in advance.

 

[Curious Chris]

Wall at 3000 rpm is usually MAF related. If it runs the same with the MAF unplugged I vote for the MAF.

The MAF is a the primary input for the ECM as pressure does not mean there is flow. All the other things you are seeing could very well mean the ECM is confused and trying to compensate.

 

[shizzler]

...but if it runs the same with the MAF unplugged, then it's not the MAF.

Thanks though. But I think I have it figured out. There appears to be enough of a kink in my rubber fuel line going to the injection pump that it could actually be collapsing under high fuel vacuum (i.e. high rpm, high demand). I have replaced my hard/clear fuel supply line from the filter to the pump after it cracked with some cheap generic fuel/transmission line hose. I think the diesel is softening it up too much. Time for something more durable.