Fuel rail pressure too low and loud bang under boost past 13 psi

[Sanzeii]

Hey VW community! It is my first time doing a thread and let me explain.

I have a 08 GTI stage 3+ APR fully built with aux lpfp and upgraded hpfp. Ive been having the Low fuel rail pressure for a while. Now, i found my boost leaks and today i believe i got em all. Once i fixed my big leaks,all of the sudden, the car starts doing a really loud bang and hard jerk movement when i wanna boost fast past 13 psi. It also showed more codes. I thought the leaks were going to solve the code for low pressure but now there is so much pressure it is making that loud bang. Cam follower is good, changed a couple of sensors, tested the in-tank pump and it is working. I can drive it without accelerating hard and if i try to go past the loud bang it just does not hold pressure and fluctuates all crazy. Im trying to include all i can for you all to help me brainstorm because it has been a while since ive had fun in my baby. Need some help. Thank you.
ps i took a video of rail pressure, injection timing, boost pressure and others while idling and pressing on gas but it does not let me attach a video.

 

[ROH ECHT]

Where is the low fuel pressure just prior to it popping? I've seen when the low pressure pumps are failing to provide ample pressure, it can pop and bang. Does your scan tool allow you to log live data for the fuel pressures? If so, you may want to log both high and low pressures while at full throttle...from near 2k rpm to redline. But if your '08 is TSI, then it may not even have the low fuel pressure sensor.

I see a fault that would be P0236/000566...and this means the ECU loses communiction with the MAP sensor. This may be the cause of it all. Might be a disrupted connection or the sensor itself is failing to report accurately.

 

[Sanzeii]

Where is the low fuel pressure just prior to it popping? I've seen when the low pressure pumps are failing to provide ample pressure, it can pop and bang. Does your scan tool allow you to log live data for the fuel pressures? If so, you may want to log both high and low pressures while at full throttle...from near 2k rpm to redline. But if your '08 is TSI, then it may not even have the low fuel pressure sensor.

I see a fault that would be P0236/000566...and this means the ECU loses communiction with the MAP sensor. This may be the cause of it all. Might be a disrupted connection or the sensor itself is failing to report accurately.

Thank you for replying back! It is an FSI! I found that the MAF was faulty as well so I swapped it. Once I swap it, now I can ride it but it still pops at about 15 psi. If I increase acceleration slowly n push it hard after, I can get to 20 psi but that's about it , it does not hold. Now the pop seems to happen mostly at hard boost in 2nd and 3rd. It is mild to none at 4th gear. After changing MAF, codes are Low rail pressure, multiple misfires and turbocharger boost sensor circ. high input. It seems to be an electrical issue but just can't wrap my head around it. Im not to savvy to do a log of pressures even tho my scanner does let me. The pressure fluctuates a lot tho I do not know what would be a proper range for it. I tested the lpfp directly (direct voltage) and its pressure while riding ( with a gauge) and it sounds healthy indeed. It is definitely a pain with this one. Cheers!

 

[ROH ECHT]

I hate giving a list of parts to swap in hopes one will eventually be the fix.
Have you confirmed the wiring to the MAP sensor (located on the pipe between the FMIC and throttle-body) is connected and its terminals are clean?
The other probable issue is the G410/low fuel pressure sensor which mounted on the side of the HPFP.

You might have a go at checking the fuses in both the dash and next to the battery. I cannot find an accurate fuse diagram to show if the G410 and MAP run on the same fuse or not. I hate the fuse diagram inaccuracy. I have eight prints for all build periods for the MK5 and the one for when mine was built doesn't match the fuses that are actually in mine....nor do any others.

 

[Sanzeii]

I changed low pressure sensor, MAP sensor as well because it was cracked and it was leaking air. Connections look good.Changed rail sensor. I will recheck fuses but doubt that is the problem. Im thinking now if the camshaft pos sensor might be bad. I hate buying blindly for a shot of luck. It feels like an electrical problem but at the same time the individual components seem to be working. Next step is looking at that cam pos sensor, i also ordered a breather hose for pcv tht was leaking air but i doubt that is causing what im experiencing. Has not been an easy find!