TDI lacking power

The lads new Tdi 75 is lacking power at around 2000 revs in every gear , it revs up and beyond 2000 to maybe 3500 and tops out. Standing start is fine, 1st gear then 2nd is good upto the 2000 rev mark but seems to loose poke for want of a better word.
After a bit of searching people have mentioned the MAF sensor, what is that and what does it do?
Anymore guesses what could be causing it?
Ta chaps.
 

Birchall

Dick Chown Award 2016
The lads new Tdi 75 is lacking power at around 2000 revs in every gear , it revs up and beyond 2000 to maybe 3500 and tops out. Standing start is fine, 1st gear then 2nd is good upto the 2000 rev mark but seems to loose poke for want of a better word.
After a bit of searching people have mentioned the MAF sensor, what is that and what does it do?
Anymore guesses what could be causing it?
Ta chaps.

Check the bottom of the intercooler to see if there is any oil present (this would indicate the seal has gone on it, causing a boost leak.

Steve B
 

depronman

Member
to answer the question John the MAF sensor is the Mass Air Flow sensor
Is is located in the upper air hose, is about 3" diameter and about 4 to 5" long, black in colour
There is a wiring harness going to it

You can try running the car without the MAF connected, the ECU will use a default map if it gets no signal from the MAF. A bad map will cause more problems than no MAF, so it is always worth trying it disconnected to see if matters improve

I certainly have at least one spare one in the garage should you need one, I have found that cleaning them never works, but you could try that if removing the plug improves the situation. Remove the MAF and use Carb cleaner in an aerosol to spray the sensor. This is easier is the sensor section is removed from the MAF housing (2 screws X head on earlier and security torx on latter)
VAGCOM may show an error on the MAF if it is really bad

Cheers,
 

Fallan

Member
Most PD engines will have remnants of oil in the induction system so chances are it will have at least some, as Steve said - check the bottom intercooler hose - these are prone to ‘popping off’ so check all boost hoses and the
Vac pipes.
 

Skipton01

Admin Team
MAFs are prone to failure as they age and one of the worst killers of MAFs are K&N air filters that are incorrectly oiled. Excess oil from the filer makes its way onto the sensing element in the MAF and will quickly render it useless. You can have a go at cleaning, but it's normally terminal. New ones are pretty pricey for what they are and I'd never bother with second hand ones from auction sites, as they could easily have failed and a visual inspection won't reveal a lot.
 
Thanks for the advice chaps.......Paul, would it be worth a try at taking the MAF of the blue breaker and trying that? I do know the engine is running great in that car.
 
I take it that this is the clip that has to be disconnected? circled in red

DSC_0146.JPG
 

Skipton01

Admin Team
Yes, that's the clip. Standard release method of a flat blade driver in the end to release the tab inside. The bigger issue is getting the light grey metal clips off. You need some manly mole-grips which you can get the clip started with, then you'll need to tighten the thumbscrew to get the clips to the point where they are wide enough to pass over the lumps in the pipe each side. Don't take them off completely though - leave them on the adjacent pipe or you'll never get the mole-grips back on!
 
Cheers Skip, just sumat else though, sorry. The two little screws (torx 20 I think) they seem to have a pin in the centre of them so stopping the torx bit from seating proper, never seen these before, is that normal ? I take it I will need something like this. (edit, just realised Paul did say security torx)

008236064476lg_1_1.jpg

Yip, I know what you mean about the clips but Ive cobbled together a pair of small gilbows that do the job so no problem there.
 
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depronman

Member
Yes try swapping from the breaker they are all the same on the tdi and the fsi


Sent from my iPhone using Tapatalk
 

Skipton01

Admin Team
I think you'll find it's actually not torx, it's a 5 point star bit that you'll need. However, if you're swapping out the entire assembly there is no need to undo the screws, just the clips and the electrical connector.
 
Ok , we have progress but not good. I had a ride up to where the lads car is in Bolton and met him, we popped the bonnet off and disconnected the wiring/clip, popped the bonnet back on and asked him to take it for a test drive, 10 mins later he came back and said it was no different so reconnected the wiring/clip.
Now here's a thing that just might throw more light on the matter, he floored the peddle in neutral and the revs went up to around 3500 but with his foot still pushing hard on the accelerator, it suddenly went right up to the red line then after about two seconds returned to 3500 ish, that cant be right. any advice on that one?
 

Skipton01

Admin Team
I was going to suggest the turbo earlier, but thought it'd be a bit off-putting and pessimistic. The turbo kicks in at around 1800-2000rpm, so right where you stated that everything was fine before. It's also possibly a vacuum pipe that's the issue - I had a limp mode recently which was sorted by adjusting the pipe to the turbo.
 

sco

Member
Surely you don't need the turbo to get the engine to redline in neutral? What about investigating the throttle pedal position sensor?

Simon.
 

Skipton01

Admin Team
Surely you don't need the turbo to get the engine to redline in neutral? What about investigating the throttle pedal position sensor?

Simon.
No, of course you don't, but it's related to the lack of power after around 2000rpm and I agree, a diagnostic would be the first step to getting the cause pinpointed. If you're able to have a pootle through Leigh and Culcheth, I can do a scan for you next week if you like?
 
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