Maf Testing?+

[Guest vinny2984]

I belive i may have a faulty maf, tried cleaning it as described on a couple of posts with no improvement.

 

does anyone know a way of testing it before i spash out on a new one only to find the problem wasn't the maf at all

[charles]

can't you ask the garage to " borrow" a good one.

[Guest Turbo]

Take it to a local garage and ask if they have a "lap top " and a pod for your engine. If they have it will read "Maf fault" if there is a problem. It`s an expensive piece of equipment and normally dealers charge about fifty quid for this check but you should get it tested for a lot less elsewhere (especially if you have cash on you ).

[Jim]

When mine went on my VW Passat, I disconnected it and the car ran "better" and revved more smoothly. Reconnected it and back to running like a dog. New MAF from GSF for

[charles]

I paid EUR 70 for a diagnosis which had no reported errors, although the car ran like a dog. conclusion of the garage:

 

"we can not find any fault, maybe there is some mechanical error or a problem with the sensors"

 

I think the problem is that de car was only checked static. They connect the car at the garage and rev it up. The only good check is connecting a laptop and driving it, logging the output, and analysing it afterwards.

[plwsm]

Hi,

Sorry for the late post but I only just found this forum (my first post)

I had a MAF go bad on me a few months ago. Initially, I used a multimeter to measure the output voltage at several RPMs and recorded the following voltages -

 

900 RPM = 1.85V (should be approx 2.2V)

1500 RPM= 2.35V (.. 2.9V)

2000 RPM = 2.56V (.. 3.4V)

2500 RPM = 2.86V (.. 3.6V)

3000 RPM = 2.98V (.. 3.8V)

 

(obviously this is going to be dependant on the exact fault - your MAF sensor may behave differently). The above was measured on a 1.9 TDi engine - I assume that the bigger cc engine air intake would give a proportionately higher mass air flow for the same RPM?.

I found it easier to measure the voltage using a pin to push through the wire insulation on the harness to the MAF (pin 5 on a Bosch MAF sensor). I found there wasn't much of a voltage drop between the MAF ground wire and the battery negative, so I used the battery for the meter common.

Still not convince that it was the MAF, I made up an OBD cable and used VAGCOM to check 'specified MAF' against 'actual MAF' and this clearly indicated that the MAF was bad. On a motorway run, specified MAF was around 650mg/R wereas actual was about 490mg/R. There were no DTC fault codes reported.

A new MAF sensor fixed all the problems.

 

One final note, only this weekend the galaxy had similar problems (lack of power). This time I had a fault code for Charge Pressure Control Deviation (P1550). This turned out to be a loose/ corroded vacuum pipe on the charge pressure control valve for the turbo. It is definitely worth checking the vacuum pipes (and the air filter) before investing in a new MAF if you don't have the diagnostics.

 

Regards

Phil