GT TDi 115PD - No Boost whatsoever! Help!

[jwalman]

Hi everyone.

Ive just bought a 2001 GT TDi PD 115 done 117k with 14 stamps in the book.

It has absolutely no boost whatsoever. I just drove it back 250 miles tonight and aside from the lack of turbo it drove well - just extremely underpowered. I had no black or white smoke, and tried stopping and switching back on, but it remained the same - so I dont believe it goes into limp mode, unless it possible for the car to be in limp mode all the time, even from start up - is this possible?

Could the MAF sensor or split pipes cause this problem? You still here a whistle under acceleration, just no power.

Max Speed is 80 - 85 MPH. It seems to accelerate better at lower revs, but its still very slow. I reckon my 0-60 would be about 20secs - maybe more. Economy was good, returning 52MPG for the journey averaging about 75mph

I understand that if the turbo was knackered there would be lots of smoke.

The car had been standing since October and not been used until today. (includes recent freezing conditions.)

I would really appreciate your help as I have searched the forums, and most people have the 'switch off and back on again, Limp Mode, MAF faulty' issue, which I dont believe this is.

Thanks.

[Simon@DTUK]

Hi mate, I believe that if it was the MAF it would throw an engine management light up on your dash and go into limp. It wouldnt get anywhere near 40 mph let alone 75-80mph if it was in limp.

It could be a number of things, First check all your turbo related vav pipes.

It could be just a split pipe,or it could be the acctuator on the turbo sticking or a defective vaccum valve-these are the 2 square shaped valves mounted on the bulkhead behind the engine to the right as you look at the engine.
Doesnt sound like its the turbo to blame.

[Talisman]

i had this with mine when i got it, it was the air flow mass meter (think thats what its called)

Cost me about £80 unplug the old one, plug the new one in, been going like a dream ever since.

[fisheggs]

With most MAF faults, it will NOT throw up a fault code. Especially the diesel engines.

I would suggest a fault scan first for anything else, but sounds like a MAF sensor. Remeber buy genuine from dealer or your local TPS.

[judgefudge]

Hi

I've the same problem on an old A4 Avant 1.9tdi - hits 80-85 mph then you feel the turbo drop off and it hits a ceiling. Let us now how you get on !!

[jwalman]

Thanks for your reply, should the turbo actuator move up and down by just revving the car? (it doesnt) Also the valves that you refer to, I have 1J0 906 627, & 1J0 906 627A printed on mine, is there any way of testing these? TPS want £29.54+vat for each, so I hope its something simple like this.

[martin1810]

The turboactuator should move about 2cm when you start the car. So you need someone to start it while you watch.

[nevo]

Very likely its the Maf next to the air filter box,you can confirm this by disconnecting the the electrical connection and driving it ,you will feel a increase in turbo boost if its faulty,this will raise a fault code on the car which will need resetting so if you need to pay to get it reset probably a good idea to just change it anyway in a car of that age, fit a genuine vw one,last time I asked it was 68 quid

[jwalman]

Acutator doesnt move on start up..... could this be the problem?? Expensive???

[MagicMat]

Im sure i've read somewhere that the Actuator can be unbolted, sprayed with WD40 and then moved about to try and free it up abit ????

[fisheggs]

Acutator doesnt move on start up..... could this be the problem?? Expensive???

Before you start spending money, get a fault scan done.

[Simon@DTUK]

Im sure i've read somewhere that the Actuator can be unbolted, sprayed with WD40 and then moved about to try and free it up abit ????

Yes you can do this and its well worth a try before you spend money:D

[martin1810]

The actuator not moving can be good news. Pull the vacuum pipe off the actuator. Add another piece of pipe and suck hard. The actuator should move. Also try blowing hard into the pipe that you pulled off the actuator. You should not be able to blow. If you can, you have a vacuum leak. Good luck.

[jwalman]

Ok, actuator fine. Ran a scan and found (obviously) the MAF sensor, and a charge pressure code (cant remember the actual code). Any ideas? I hear that they always throw up the MAF code regardless of whether it needs replacing or not. I had a Passat 115 before with the usual problem where it goes into limp mode, changed every sensor under the sun, and it turned out to be a vacuum hose that had popped off! Before I change the MAF is it worth checking anything else. All pipes have now been checked.

[nevo]

Eliminate the maf first its the most likely and least expensive,its very simple just unplug it and drive it!!!, this small device can have a dramatic effect on the cars performance if its gone bad.

[jwalman]

Yep, Ive already done that. Disconnected it, and it drove exactly the same. Does this mean its not worth investing in another MAF?

[nevo]

Forget the maf now concentrate on the vac pipes to the turbo actuator and n75 valve on the bulkhead (the righthand one as you face the rear of the vehicle)check for blockages in the pipes,blow them throught,get hold of a vac pump and test the movement of the turbo actuator,check and see if the n75 valve is ticking(screwdriver to the ear).Could be the turbo is caked in carbon and stuck in one position,so check that actuator see if you can get it moving,removing the turbo is a big job so you need to eliminate the vac pipes and the n75 valve first, if any doubt about the vac pipes renew they're cheap.

[martin1810]

The charge pressure code is vital to diagnosis. I bet it was pressure too low in this case. Disconnecting the MAF doesn't tell you anything. When the MAF is faulty or disconnected the ecu uses a set of inbuilt figures and carries on with lower performance. (which is what you have). Change the vacuum pipes, clear all codes and scan again. If performance is still down but no codes, the MAF is probably faulty.

[MagicMat]

I have a MAF sensor off a GT TDI 115 AJM that you can have for £20 delievered.

Only reason i changed it was because i thought it would help cure my recent problems but it didnt.

Pm me if your interested

Matt

[nevo]

On maf disconnection the ecu does indeed revert to a predetermined boost, but in my experience you can notice a slight increase in power,eventually you'll have to bite the bullet and spend some money, 20 quid for a maf aint bad.

[jwalman]

Yes it was the MAF after all that!!! flys along now!! Shame I didnt read your message before Matt, I would have had that off you. thank you everybody for all your help.

[MagicMat]

Yes it was the MAF after all that!!! flys along now!! Shame I didnt read your message before Matt, I would have had that off you. thank you everybody for all your help.


No Problems mate :)

Glad you've got it sorted