2000alhVW
Veteran Member
My car has suffered from low power for a long time.
The symptoms are.... no power. That's it. No noticeable black smoke or soot (it does smell a bit strong though), and no obvious issues. Someone like my mother could drive the car indefinitely with no complains other than "its VERY slow". Very hard to trip a DTC. When it does trip, it is P1556.
I have a VCDS. At very low throttle, the car does okay. And the measured vs actual MAF values stay kinda close. Anything more than 20% throttle, and they deviate wildly. When increasing throttle, the actual MAF reading will decrease. I read an article on KermaTDI that might answer why - when the computer senses an underboost issue occurring, it cuts back fuel. So basically, as I try to increase throttle, the computer cuts even more power.
Things I've done:
At this point, I feel like my issues are narrowed down to an actuator, turbo vanes, or a boost leak.
If I'm missing something, please correct me so I can add it to the list of things to check.
I plan on doing the easiest thing first, which is spraying the actuator with WD40 and then looking more closely at it. After that, I feel like the easiest thing is to check for boost leaks.
Is it possible to do a sort of at-home smoke test?
The symptoms are.... no power. That's it. No noticeable black smoke or soot (it does smell a bit strong though), and no obvious issues. Someone like my mother could drive the car indefinitely with no complains other than "its VERY slow". Very hard to trip a DTC. When it does trip, it is P1556.
I have a VCDS. At very low throttle, the car does okay. And the measured vs actual MAF values stay kinda close. Anything more than 20% throttle, and they deviate wildly. When increasing throttle, the actual MAF reading will decrease. I read an article on KermaTDI that might answer why - when the computer senses an underboost issue occurring, it cuts back fuel. So basically, as I try to increase throttle, the computer cuts even more power.
Things I've done:
- Replaced MAF. Bought new Bosch MAF off eBay. zero change. I also grabbed an unknown MAF (OEM Bosch) from the junkyard and put that in. Zero change.
Unplugged MAF - trips "MAF ground fault" CEL, and regains some power - Replaced all vacuum lines with quality material from IDparts
- Swapped my N75 valve with N18 valve, zero change. Went to junkyard, grabbed unknown N75 & N18 valves, swapped them in, zero change.
- Vacuum tested the system and determined it properly holds vacuum. I have applied vacuum to the actuator (w/MityVac) and confirmed actuator rod movement. I did not measure the movement to confirm 3inHg-18inHg.
- Visually examined my intake manifold. Very little buildup on the walls.
- Replaced fuel filter.
At this point, I feel like my issues are narrowed down to an actuator, turbo vanes, or a boost leak.
If I'm missing something, please correct me so I can add it to the list of things to check.
I plan on doing the easiest thing first, which is spraying the actuator with WD40 and then looking more closely at it. After that, I feel like the easiest thing is to check for boost leaks.
Is it possible to do a sort of at-home smoke test?