Low power - maf?

[Mad_Dasher]

2003 jetta tdi 5speed with 108 miles. Low power all the time - not limp mode. I have checked the VNT cycling using vagcom - it works. Intake and snow screen recently cleaned. Question: my maf is only showing 50% of specified value during acceleration. I have tried using a good maf but the result was not any better. Could a turbo that is not working and, therefore, not sucking air into the engine cause the maf to read low?

 

[justynd]

I would recommend checking vacuum lines and function of the actuator. It should move with a strong push of the finger. This may be a bit uncomfortable. Put a hand vac pump on the line, like a mity vac, and it should start moving at like eight inches and stop at eighteen. Search for actual specs, but they matter a lot and it should hold vacuum.

 

[justynd]

Also, unplugging the maf puts it in a default mode. If there is a notable difference with it unplugged, that may be your problem. I've recently replaced my maf and it routinely reads far different than specified values but the car runs fine. I'd say UN plug the maf after it being at operating temp and drive it hard. If there is a difference you may be on to something. Otherwise checking vacuum and movement of the actuator would be my second step

 

[Mad_Dasher]

Thanks, I did find an answer to my question. I disconnected the vacuum line to the turbo actuator on a second Jetta that was working. With the turbo not working, the maf suddenly fell to about 50% of specified.

 

[keaton85]

did you run a boost graph with VCDS?