MAF question

The passat has a low power / stumble over 2k rpm, so I made a log file with vcds. One thing I noticed right away was the requested for mass air flow is 1000, dosent matter if the engine is warm or cold, or rpm. Is this normal? If it is not normal where should I start looking?

The car starts and runs good below 2k, and above 2k if I accelerate slowly.

I ungnplugged the MAF sensor and it did not change how the car runs, I also did not get a check engine light with the MAF unplugged. A ran a scan with VCDS and nothing about the maf being unplugged.

Your car has a tune with an EGR and MAF delete... When requested MAF is an individual number like that (typically 850 mg/st or 1000 mg/st) and never changes, the computer is effectively ignoring all inputs from the MAF. It has a "speed density" tune and is judging how much fuel to inject based solely on throttle input and MAP sensor feedback (manifold pressure instead of mass air flow...).

So Matt, is it good or bad to have the MAF deleted? What is the purpose?

Matt-98AHU said:

Your car has a tune with an EGR and MAF delete... When requested MAF is an individual number like that (typically 850 mg/st or 1000 mg/st) and never changes, the computer is effectively ignoring all inputs from the MAF. It has a "speed density" tune and is judging how much fuel to inject based solely on throttle input and MAP sensor feedback (manifold pressure instead of mass air flow...).

Click to expand...

Thanks for the input, this is great stuff. I really need to get a VCDS and learn. This prompted me to retrieve a pre tune picture of the Polar FIS read on the MAF. I have to see if the tune (Kerma on mkVI JSW) did a "speed density" mod (eliminate reading). That kind of bothers me if so.

pre tune


BTW I don't really understand when looking at the (2) different "group 3" MAF columns (?) and one is the mentioned 1000 non adjusting value & the other averages around the low 400's @ idle.
* why are the 2 columns diferent?
* why is my MAF around 250 @ idle and the posted column around 450?

zzdiesel said:

So Matt, is it good or bad to have the MAF deleted? What is the purpose?

Click to expand...

It's fine. It means the EGR is disabled, as the MAF is the primary feedback for the computer to judge how well the EGR is open.

Sometimes having a MAF delete may mean a slight bit more delay in throttle response due to how the computer calculates how much fuel to inject and when, but since these hot film MAFs are pretty sensitive and tend to start underreporting air flow at some point in their life, it's eliminating the MAF as being a contributor to drivability or power reduction problems. So, not necessarily a bad thing.

Thanks for the info, that answers that question.