[wheela]

Originally Posted by learjet23a

Well, not sure if any of you are interested but I did successfully replace the entire head on my N55. It was an incredibly difficult job with the engine in the car but I muddled thru it. Worst part was the machining of 3 holes I needed in order to fit the newer style recessed spark-plug inserts!

Car runs great only issue is I'm right back where I started with this damn 28A0 (P112F). Ista did give a brief Lean code not sure if that might lend a hint. I guess I can rule out the head and internals this time round.. Any idea where to go? I have thoroughly smoke tested the intake and crankcase. Inspected and cleaned the MAF/TMAP and throttle body and preformed adaptations in ISTA as well as the fuel vent disconnect.

Glad to hear you got the head swapped out and are up and running again!

For that 28A0 code, you probably already know, but I believe that's a plausibility code where the mass air flow into the engine as measured by the MAF sensor doesn't match the expected mass flow calculated from values from the MAP and/or TMAP sensors & throttle position (the plausibility check of the MAF reading). Is all your hardware stock? Not sure what all you've checked, but I'd look for anything that could cause a discrepancy between the MAF readings and calculated mass flow from the map sensors & throttle body position. If you're confident you have no vacuum or boost leaks, and are running stock hardware, maybe look at the MAF and two TMAP sensors and their electrical connections? And same for the throttlebody?

Edit: Can probably throw valvetronic position in the mix as well, since that's effectively another throttle plate in the plausibility calculation for air mass flow into the engine. And intake cam position...

[learjet23a]

Yes I'm completely stock.. Ok I will have a good look at the Maf/tmap/map throttle body. I have inspected the plugs and cleaned all the sensors, is there another way to test these parts? I think I saw on some videos they back probe them with a waveform oscilloscope, don't think I have one of those lying around...
No boost leaks or Vacuum leaks that I can see i have smoked the crankcase and intake, tight as a drum under there.
If valvetronic position was an issue how would one go about looking into that? Would I not get some codes related to it?

[learjet23a]

I have also heard that the old HPFP could be a cause for this error, no idea how exactly ... I have the older Conti pump, certainly no fuel codes and I have instant starts no long cranks.. thoughts?

[wheela]

Originally Posted by learjet23a

Yes I'm completely stock.. Ok I will have a good look at the Maf/tmap/map throttle body. I have inspected the plugs and cleaned all the sensors, is there another way to test these parts? I think I saw on some videos they back probe them with a waveform oscilloscope, don't think I have one of those lying around...
No boost leaks or Vacuum leaks that I can see i have smoked the crankcase and intake, tight as a drum under there.
If valvetronic position was an issue how would one go about looking into that? Would I not get some codes related to it?

Sorry, not sure of any good way to test these components out. You could disconnect, clean the contacts and see if it resolves anything, but that obviously only checks the connections. Also not sure how to check valvetronic position, I believe the position encoder is built into the valvetronic motor. I'm guessing valvetronic isn't the issue though. I think you're right, I think there would be codes for valvetronic if that was off.

About the hpfp, I can't see how that could relate to this issue?