1.9 tdi not fully boosting......

[peterb107]

I`ll try once more......had no replies last time


Right, my problem is this - I have a 1.9tdi sport, but she is no longer giving me full boost (i have no boost gague, it just feels a lot less powerful)
Also, i get put into limp mode (even when doing 70 @ 2.5k revs on flat road??)

I have tried unplugging the MAF, but the car is awful with it off, so I think that rules the MAF out.

Could it be a boost leak? - (which tubes/pipes most common?)
Would faulty N75 cause this?
EGR valve?

It is REALLY doing my head in....and I know its gotta be something simple!!

If anybody within 75 miles of Cardiff has a vag-com that they could check my car out with, or any ideas on this, I would be very very grateful.

Thanks for looking.

 

[sssstew]

peter, want me to move this to the TDI section for better response?

You say 1.9 TDI sport but they didnt do that model in the mk2 in the UK, so do you have a MK3 TDI Sport?

 

[peterb107]

Didnt realise there was a specific tdi section.....yes please!

I`m certain my car is a mk2?!?! maybe just s then not sport?

Thanks

 

[M1KEH]

It will just be an s. I'll be in Bristol after the 20th of September with vag-com if thats any help. I would check the small hose from the inlet to the ecu for leaks first.

 

[Deleted member 32025]

My egr valve is stuck closed, or according to vag-com it is, but mine still drives fine it just means no exhaust gasses are getting recirculated.

I would check all the pipes too from the airbox down to the intercooler, and back up to the inlet manifold looking for loose connectors and cracks. If it is leaking boost you will probably be able to hear it whistling alot more I would assume. I have managed to take all the pipes down to the intercooler and to the inlet before, its quiet easy.

Also you meantion limp home mode, now this can be causing by the turbo overboosting as there are vacuum pipes that go down to the turbo and your ecu reads the pressure.

I find the mk2 forum to be more petrol beffa's because there more common, a good tdi forum is tdi club, its American based but there's pretty much every piece of information you want on tdi's and somebody will more than likely help you becuase it is a massive forum.

 

[peterb107]

Thanks for the reply, yes, definately whistling a bit (more of a whooshing sound)

I am definately no mechanic......so please excuse me if I sound dumb!!

I have checked every pipe and hose that I can see starting at the MAF, then down to turbo itself.
The one from intercooler up seems fine, as does the one that goes towards the passenger front wheel.

Then there`s the 2 thin red and blue rubber hoses that go from turbo to the (N75?).......These are very difficult as the rubber is obv covered. This may sound daft....but my red hose was once cut between the turbo and n75 (but has a 100% reliable join now), Anyway, I disconnected at the join and blew down the red pipe towards turbo (about 12" from turbo).....The air was definately escaping, it was like blowing down a drinking straw.....now, Im not sure whether I was just blowing into the turbo, or what, as I could feel no air escaping down the pipe, even at join with turbo??? But should this happen?

I am at a total loss with this.........It drives ok, but why settle for my turbo only working about 30% when I know what she`s capable of!!!

Could it be a stuck wastegate or acuator (dont know if it has one) - where would I find, and how could I repair??

Many many thanks again

 

[Deleted member 32025]

Well based on the fact that the car some times boosts and sometimes doesn't i cant see that it is a boost leak becuase if it was, it would just never get any boost at all, so it could be electrical maybe a loose connection or the thing that reads to turbo pressure to your ecu is not working (N75 as you called it?)

If its not intermitent and there's no cracked piping, it could be your intercooler. That will be placed far left corner behind the bumper infront of the front wheel, you will be able to see it through the lower front bumper.

i would probably start by getting sombody with vag-com to have a look, see if there is any fault codes on the ecu.

 

[sssstew]

agreed, and get some logging done, MAF and Boost requested vs actual and graph it and lets see.

 

[M1KEH]

I'm happy to do fault diagnosis and logging when I'm back in Bristol.

 

[peterb107]

I would appreciate that....how much will it cost, please? (after 20th was it?)

Going back a couple of replies........its not that my car sometimes boosts, and sometimes doesn`t. It is always the same. Probably only giving 20-30% of what it used to though - as I said, Im far from being a mechanic, but i presumed it must be a small leak - therefore not building enough pressure to give full boost?? (probz completely wrong lol)

I have owned this car/shed for 4 months - and only had 3 days without some sort of fault or annoyance! - It`s not that I`m THAT bothered about going fast or whatever - its just KNOWING what the car is capable of and KNOWING theres a fault!

 

[M1KEH]

Won't cost you a penny, I enjoy tinkiering. Yep after the 20th. Ill let you know for definate though.

 

[Russhowe]

I would appreciate that....how much will it cost, please? (after 20th was it?)

Going back a couple of replies........its not that my car sometimes boosts, and sometimes doesn`t. It is always the same. Probably only giving 20-30% of what it used to though - as I said, Im far from being a mechanic, but i presumed it must be a small leak - therefore not building enough pressure to give full boost?? (probz completely wrong lol)

I have owned this car/shed for 4 months - and only had 3 days without some sort of fault or annoyance! - It`s not that I`m THAT bothered about going fast or whatever - its just KNOWING what the car is capable of and KNOWING theres a fault!

I think i've got the same problem mate, I've got a Toledo II 110 (ASV engine)
when i used to floor it hard an any gear, let's say 3rd at 1200rpm, there would be a delay (the turbo spooling up) and then the boost would come on hard and fast and would really push you back in the seat. Awesome feeling

NOW, while it still boosts, it comes on much more softly and smoother. I dont have any limp-home mode kicking in. And my vag-com returns no codes at all.
I've not got any abnormal hissing from anywhere to suggest a boost leak. (would sounds like a tyre going flat whilst the engines running - if that helps describe it ha ha)
I've ordered a boost guage and provided it arrives in time will be plumbing that in over the weekend to see what pressure my turbo's producing.
Does anyone know the factory figures?

Possible causes i've been suggested are:
*Waste gate stuck open ever so slightly
*Actuator rod come undone reducing boost
*EGR valve problem
*Veins in the turbo (Variable vein turbo) clogged
*Fuel pump over-fuelling, thus the turbo boosting harder to compensate. now due to use has calmed down.

I'm keeping this thread in my watch list as i'd love to hear what your vag-com session comes back with, results wise. I only have the shareware version, with a cable bought from ebay... enough to read and clear codes and basic functions.

Russ'

 

[S7UYJ]

I've had a similar problem... Double check the 90 degree elbow pipe coming from the top of the intercooler. check the metal lugs on the end of the pipe for damage... basically what happend to mine was that it popped off, damaged the lug and now leaves a gap where it is half pulled out.
problem is though when the engine stops, the spring effect of the pipe and where it is pushed the pipe back in so it can look like its fine, untill you boot it and build up the pressure!
is there much black smoke?

 

[Russhowe]

presonally i've not got any smoke, clean and clear as far as i know
dunno about peter though.......

peter?

 

[Seatmann]

I had the same problem but all is cured. Take off your turbo and connected pipes and intercooler and give them all a good clean. Also the inlet manifold which is probably clogged with black gunge. Make sure the waste gate acuater moves freely unless you have the garret in which case you might need further info on the way they operate. Mine is a kkk turbo but I know a lot of the vw's have garret vnt. I also replaced all the vacumn pipes to and from the turbo and various solenoids and finally a nice new air filter. My car has never run so good. There is a lot of info on cleaning turbos and manifolds on the tdiclub.com site. Hope this helps. Ps My car didn't smoke and still doesn't.

 

[Russhowe]

I had the same problem but all is cured. Take off your turbo and connected pipes and intercooler and give them all a good clean. Also the inlet manifold which is probably clogged with black gunge. Make sure the waste gate acuater moves freely unless you have the garret in which case you might need further info on the way they operate. Mine is a kkk turbo but I know a lot of the vw's have garret vnt. I also replaced all the vacumn pipes to and from the turbo and various solenoids and finally a nice new air filter. My car has never run so good. There is a lot of info on cleaning turbos and manifolds on the tdiclub.com site. Hope this helps. Ps My car didn't smoke and still doesn't.

not the answer i was hoping for. ahh well.
Thanks Seatmann

 

[mikeyibiza]

do you do lots of shortish journeys? maybe worth burning half a tank and going for a long drive, really clear it out! this worked a treat on my friends a4 tdi. it was from cornwall to london nearly but it was a world of difference afterwards.

 

[Russhowe]

my trips are mainly from lampeter to Carmarthen (about 25 miles each way - with varying roads, tighter and intricate lampeter side, getting more open and more throttle availablility closer to carmarthen.)

my normal shift point is approx 3000rpm and i've got a heavy right foot so there are plenty of times where my foot is flat to the floor especially when overtaking.

I was playing around with the car today working out how to fit my boost gauge (not keen on the idea of drilling into the olid boost pipe)
i hooked the laptop up with vag-com (basic) and started logging.
results in 4th gear, 1500 to 3000rpm (mild uphill):
http://i260.photobucket.com/albums/ii16/masterblaster20006/Y48GNYturbomap.jpg

 

[sssstew]

you need to go around to at least 4k rpm really.

 

[Seatmann]

Believe it or not my car actually had an over boosting fault according to the ecu. (A mate runs a garage close by and plugs up my car for cheap) which gave me a lack of POWER. Go figure. If you could even get just a fault code you could look that up. Have you asked any local garages? It doesn't have to be a dealer.