MAF Logs - help needed

[shazzydoosh]

Hi all,

I have been experiencing a loss in economy recently, and my engine has been sounding more "throaty". Some people have pointed out it could be the MAF.

I drove the car with the MAF disconected for a day or two, severe power drop but a lot smoother, and better MPG.

I managed to log the MAF today (actual Vs specified) along with a load of other blocks in VAG com. Problem is, I have no idea what to look for (i.e. when it is out of spec). I have plotted it onto graphs showing engine speed, specified MAF, Actual MAF, and Actual -(minus) specified).

What it shows is about a handful of occasions when the Actual MAF is higher than the specified by a large amount (but only a handful), and a couple of occasions where it is significantly lower. The rest of the time it is hovering around the specified by +or- 30.

Is there anyone out there who can intepret my logged data or my graph. The spikes are so intermitent that they wouldn't account for the constant throaty sound, but the rest of the time it hovers + or - 30, is that normal??

Just dont want to fork out for a new MAF if it is working.

Any help would be much appreciated....

 

[sssstew]

yep post up the data and i can check it.

 

[shazzydoosh]

Cheers. here is the graph:

Hope the above link works, i cant figure out how to attach pics in here. Basically, the Red line is RPM (right hand axes). The Light blue and dark blue lines are the specified and actual MAF values, and the yellow line I added is the Actual - (minus) Specified MAF. So when the yellow line spikes up, the MAF was higher than specified, when it spikes down, it was lower than specified.

Too much logged dat to paste into here... if you want I can email you the file or upload it somewhere (if you tell me where to upload it lol)

Cheers

EDIT - the X axis is time in seconds from 0 to 410 seconds (how long I was logging)

 

[sssstew]

it doesnt look to bad to me, its never really below whats being requested so its doing its job, you havent done a complete log as you stopped at 3k rpm, go right round to 4k next time, so start at low revs then full throttle accelerate to 4k then drop back, do the same again then compare the log. Usually 2nd or 3rd gear is best for it. Its not as good as a new item which you would see a higher actual than whats being requested.

 

[shazzydoosh]

Hmmm

If it's not the MAF, then what do you think could be causing my hoarsy sounding engine, and lower economy? I just thought the MAF was the problem as things were smoother when it was disconected... a lot smoother.

Will try to log some more data, but really hard trying to log in a certain gear when driving by myself

 

[Neo_VR]

Have you had it serviced recently?

Air filter and fuel filter can have a dramatic effect on economy... normal service intervals the airfilter is only replaced every 40k!

 

[shazzydoosh]

Yep, All the filters (air, fuel, oil and pollen) been replaced in the last 6months

So is everyone agreeing the MAF isn't the problem?

 

[volkscraft]

Check Valve timing, Fuel pump Dynamic timing. Could do with knowing what engine it is exactly......

 

[shazzydoosh]

cheers for the reply volkscraft

When you say what engine, you mean code? It is an AHF. Also put that on the graph. But is there anything else that defines engine???

Got a new MAF coming anyway from Seat in Plymouth (£62 for new style aparently).

Wouldnt know how to check valve or pump timing as not mechanicaly minded at all. Are they related to the TDI Timing feature of VAGcom? I checked the TDI Timing and my car was in the spec's for the engine type (according to VAGcom)... between the average and the advanced line (but not outside).

When I popped the bonnet the other day I noticed quite a few air bubbles in the fuel line going into the engine... is that normal? wasn't a huge amount, but lots of little ones.

 

[sssstew]

a few air bubbles in the line is normal.