low boost pressure? found problem... help!

Post by **alexperkins** » Sat Oct 27, 2007 7:18 pm

Mass flow air sensor is an exhange part from vdub if you choose to get it direct, so its cheaper

david burton · Post by **david burton** » Sat Oct 27, 2007 7:27 pm

how much as an exchange? the guy at the place where I went says he can get a bosch one for trade price for me (works out about Â£50).

I might try to swap out a sensor for another car's sensor..... if I can find one! no point in doing the MAF if it's not actually the problem.

anyone got a 9N 100 TDI, and fancies helping me out for 30 mins?

Post by **alexperkins** » Sat Oct 27, 2007 7:28 pm

Ill find out monday. Can ya PM me your chassis number or Reg so i can find the vehicle specific info

ceedubya · Post by **ceedubya** » Sat Oct 27, 2007 8:14 pm

I've got a clearer picture of the symptoms though - it's under full throttle that it decides to give less boost. If I accelerate under 50% throttle it's actually faster than full throttle.

have you checked for any boost leaks ???

david burton · Post by **david burton** » Sat Oct 27, 2007 10:00 pm

yeah, a cursory glance and squeeze of all the pipes I could get to.

I've had a thought that perhaps there's a small crack that only opens up under heavy pressure.

any ideas?

It's still very driveable if a little frustrating, so I wonder if the best procedure (and cheapest), is to wait until the problem is more noticeable and easier to diagnose.

I've heard it could also be an "N75" or something.....

Post by **alexperkins** » Sat Oct 27, 2007 10:19 pm

There is a possibility that one of the turbo seals is leaking - this is a common fault on TDIs. It happens to passats and golfs all the time!! Its often where the intercooler hoses join to the intercooler top and bottom. Perhaps its worth checking out?

ceedubya · Post by **ceedubya** » Sat Oct 27, 2007 11:42 pm

david burton wrote:yeah, a cursory glance and squeeze of all the pipes I could get to.

I've had a thought that perhaps there's a small crack that only opens up under heavy pressure.

any ideas?

It's still very driveable if a little frustrating, so I wonder if the best procedure (and cheapest), is to wait until the problem is more noticeable and easier to diagnose.

I've heard it could also be an "N75" or something.....

most leaks i have found are the pipework from turbo to the intercooler as they get the intial whack of boost

i use a similar ( homemade) bit of kit like this to check for boost leaks=
http://www.modshack.info/Pressure.htm

david burton · Post by **david burton** » Sat Oct 27, 2007 11:43 pm

cheers alex, might have a gander at that once I get the time

chris4500uk · Post by **chris4500uk** » Sun Oct 28, 2007 11:16 pm

Sounds like it could be a fueling problem?

I'm no expert like

david burton · Post by **david burton** » Mon Oct 29, 2007 11:36 am

ceedubya wrote:
david burton wrote:yeah, a cursory glance and squeeze of all the pipes I could get to.

I've had a thought that perhaps there's a small crack that only opens up under heavy pressure.

any ideas?

It's still very driveable if a little frustrating, so I wonder if the best procedure (and cheapest), is to wait until the problem is more noticeable and easier to diagnose.

I've heard it could also be an "N75" or something.....
most leaks i have found are the pipework from turbo to the intercooler as they get the intial whack of boost

i use a similar ( homemade) bit of kit like this to check for boost leaks=
http://www.modshack.info/Pressure.htm

thanks for this, might ring around and see if anyone has once locally.

out of interest, am I damaging anything by running with it? I wonder if it's worth me waiting for the problem to become more noticeable.

david burton · Post by **david burton** » Mon Nov 19, 2007 8:02 pm

FYI, I think this was crap fuel causing the problem, as eventually it gradually went away. some fuel cleaner and a couple of tanks of tesco (rather than the dodgy local one) and it's back to normal.

anyone else had crap fuel?

Post by **alexperkins** » Mon Nov 19, 2007 11:37 pm

Ive had a few bad batches of V Power - made the car chug like a diesel was rather scary. Its amazing really how many issues bad fuel can provoke!!

david burton · Post by **david burton** » Mon Jan 14, 2008 10:41 pm

going to resurrect this post, full throttle now seems to give hardly any response at all, whereas 10%-20% throttle picks up nice and cleanly.

must be something causing this

david burton · Post by **david burton** » Sun Mar 02, 2008 4:45 pm

I think I've found the issue here after a thorough root in the engine bay.

The cyan dotted line is a pipe leading to the turbo, but for some reason the bloody thing is routed between the air intake and the EGR pipe from the exhaust. Hot pipe = burnt pipe.

And pipe:

how easy is this to change? it looks like the pipe going to the control unit is glued / integral to the unit? should this really be routed here?

and would a break / defect in this pipe cause the symptoms?

david burton · Post by **david burton** » Wed Mar 05, 2008 1:48 pm

Can anyone help here? I've contacted VW and they say I have to buy the whole unit even though I only need the one pipe!

It's pipe no. 6 and runs from the top mount control box down to the "charge pressure control unit"

Also, can anyone confirm the route for this pipe?

Cheers!