Odd power loss

[Hoffer]

So I've noticed that lately my mileage has gone in the crapper. In addition, there was a hesitation in 2nd at about 3500 RPM, and in 3rd power would fall off a little past 3000 then seem to come back a little around 4000 before shifting to 4th. Being curious, I took VAG-COM out with me this evening, and the results are not really surprising:

So, what do you know? Turbo is mysteriously falling off as is intake air. Recent service performed (all done by myself):

Timing belt replaced
Intake cleaned
EGR delete (don't want to have to do the intake again )

Any ideas on why the turbo would stumble and fall off? Bad MAF? N75? Vacuum leak? I'm going to take VAG-COM out again tomorrow and see what it looks like in 4th at WOT. I don't notice anything in first because the turbo doesn't have a chance to poop on me...

 

[Bookerdog]

Shall we all chant it? MAF MAF MAF!

See all the flat spots in that graph?

They all point to a spotty MAF.

Good lord, did I really just do a rhyme in a post? If you've not replaced your MAF recently, you'll be pleasantly surprised by the fact that they have indeed redesigned the part, and it's far more robust now.

 

[Hoffer]

Shall we all chant it? MAF MAF MAF!

See all the flat spots in that graph?

They all point to a spotty MAF.

That was my initial assessment. I just didn't know if the MAF could affect boost like that. I thought maybe the lack of boost was affecting the MAF readings...

If you've not replaced your MAF recently, you'll be pleasantly surprised by the fact that they have indeed redesigned the part, and it's far more robust now.

Never. About 100,000 miles, with plenty of abuse (including numerous brisk gravel rally's. POR last weekend was _great_! ). I'm suprised it lasted this long. I haven't been active much on TDIClub for a couple years now. Last time I was following this stuff, the Peirburg/Mercedes MAF was the hot ticket. Is this newly redesigned one the same as the Bosch OE MAF that's available on tdiparts.com, for example?

 

[Bookerdog]

Yep, that's the new one. Significantly fewer failures reported with that one.

I just went through my first MAF replacement about 2 weeks ago. Thankfully I had the years of people complaining about it on the club to fall back on, because the car's behavior sure was strange.

Mine was a slow burn failure, with MPG's dropping for a while before I had any noticeable drivability problems. I'm working through my first full tank after the replacement and I look to be up 5 mpg so far.

It's easy enough to tell if it's the MAF. Unplug it and drive around. If it runs the same or even a little better, that's your problem. If it runs much worse, there's something else going on.

 

[Hoffer]

It's easy enough to tell if it's the MAF. Unplug it and drive around. If it runs the same or even a little better, that's your problem. If it runs much worse, there's something else going on.

Hrm, I failed to mention that. I did that test and it's much worse with the MAF unplugged. Damn near undriveable, as far as I'm concerned. That's what triggered this post. I wasn't sure it was the MAF...

 

[Bookerdog]

Dang. Well, my initial suspicions may not be correct then. I'm not a VagCom expert, but I know I've seen a different sort of MAF logging that tends to show if the values coming from there are correct. Perhaps post a query in the VagCom forum to see if anybody knows exactly what you should be looking for.

 

[troutski]

Maf

My dealer replaced the MAF yesterday. 68K miles. Today, it failed again. Took it back. They say they will not work on it due to my use of B100....

So between yesterday and today, they had a change of heart? And this is a redesigned MAF?

I think I have quite a battle on my hands....

 

[tongsli]

M,

Check the play on your turbo's actuator rod. Make sure there is play and it moves freely.

If this is the original MAF, it wouldn't hurt to get a new one. Make sure you buy the VW MAF revision C? or whatever number is the latest version. John has them.

But, check the turbo actuator.

Lito

 

[Hoffer]

M,
If this is the original MAF, it wouldn't hurt to get a new one. Make sure you buy the VW MAF revision C? or whatever number is the latest version. John has them.

Well, I did replace the MAF (got a new one from Impex). The new Chinese replacements sure are less expensive than the Bosch. Hope they last... Anywho, it seems to have gotten rid of my odd power loss (i.e. the weird turbo cutting out issue). I'm guessing that the MAF was reading off just enough to confuse the boost control...

But, check the turbo actuator.

Checked. It move some. Don't know how much is normal, but it doesn't appear to be jammed. I still have a significant loss in mileage. Even after replacing the MAF, I have yet to break 40 MPG.

Does removing the EGR completely confuse the ECU enough to completely blow fuel mileage?

I was also going to ask how unusual it would be not to get a CEL after doing the EGR delete. Ran for about three some weeks now with no CEL. But it came on this morning on the way to work. I'll have to scan it on the way home to see what it says.

- hoffer