VW T4 2.5 TDI ACV lack of power

I have got a VW T4 2.5 TDI with a lack of power, engine code ACV. It had fault codes relating to the engine coolant temp sensor and also the fuel temperature sensor inside the fuel pump. Both the sensors have been replaced and the fault codes cleared, I have adjusted the pump timing as it was along way advanced. Low rpm it now feels better but is still flat up through the rev range, no turbo operation.

I have disconnected the MAF and that makes a slight improvement.

Looking at the measure values saved at 2326rpm air mass calculated 850mg actual 430mg charge pressure 1836mbar actual 1071mbar. With the MAF disconnected the actual air mass defaults to actual 550mg. It appears that there is a low air mass, this requires fixing and it will hopefully fix the turbo fault.

The air filter was blocked so that has been replaced, no improvement.

The inlet track is all okay no air leaks. The turbo impeller spins freely. The waste gate moves okay. The EGR valve is seated correctly.

I'm still not convinced that the MAF is okay and might try replacing it, the other think is I'm wondering if there is too much back pressure, a blocked exhaust but it's going to be hard to separate due to being welded.

Any advice appreciated.

Could we have an autoscan please (see below) so we can have a collective look at what's exactly happening.
Otherwise, good info with respect to the values.

Hi iichel thank you for the reply.

I haven't got an Auto Scan saved for this vehicle, I will do a full Auto Scan tomorrow. This is the scan for the engine control unit before the repair. After clearing the fault codes and road testing only the fault codes 17664 and 17571 returned.


Cheers Colin.

Okay this morning I managed to get the cat separated from the down pipe, the air mass now reads correctly and I have the correct charge pressure and it now goes over 30mph Too much back pressure in the exhaust system as I had thought is the cause of the complaint.

Cheers Colin.