A6 1.9tdi loss off boost/power @ 70mph ish

[evomaster3000]

A problem has started to occur on my 1998 A6 1.9 TDi, when i'm on full throttle at about 70ish the boost goes and it's asiff it goes in to limp mode or something and will not boost up and pull like it did.

I've checked for loose vacuum piping as this usually causes the tubo to stop spooling up but everything is fine it seems, and i regain normal power and boost if i simply switch off and re-start the engine and all is fine until i boot it again at speed.

is it the maf?, i don't have access to a vag-com thing but i'm sure it would throw up something anyone local to the bristol/somerset area who could help.

Many thanks, jack

 

[inigoj]

MAF and sticking vnt mechanism are the main culprits.

 

[evomaster3000]

I just vixed my Boost guage and i think i found the problem, it seems that the car is sometime over boosting when i stick my foot down she's slower than usual to spool up and then it'll go to 20psi and stay there sometimes when usually it would drop back to 12-15psi.

I think this boosting at 20psi is causing it to go in to limp mode as 20psi is quite high and beyond standard factory settings and in 5th it's putting most strain on the engine etc.

I'm thinking VNT likely cause as the MAF was changed 4 years ago and has only done about 30,000 on that one, oh she's on 167,000 so VNT may need a clean i recon.

 

[yabbadoo]

sounds like your vains siezed in the turbo you can remove turbo and strip down and free up but normally its a new turbo