Poor Performance

[flandm]

I have a 2001 B6 1.8TQ with 117000 miles on the clock.

Recently I have been getting intermittant Turbo boost now there is nothing at all. The Turbo still spins up and makes all the right noises but does nothing to performance. There are no fault codes logged, no oil in the exhaust and everything else seems normal. I have checked for leaking pipes but there is nothing obvious and certainly no noise associated with a split pipe. I am starting to think its the dump valve.

Any thoughts.

Thanks

[pauldazzle]

MAF & DV would be my first things to check.

[flandm]

I did consider the MAF but the last time this failed (another car) it was associated with irractic fuel comsumtion. I will disconnect it and see what happens.

[flandm]

Fuel consumption has remained about the same pre and post lack of turbo boost if that makes any differance.

[arman123]

Could it be the map sensor?

[bodgerbob]

Have you had the vehicle scanned for fault codes, this is the best way to save money and not fit parts that are not needed, Yes it is not the answer to everything but it it narrows down the options, A good VAG speacialist will help you out, my theory is the N75 this controls the turbo check for leaking vacum hoses. hope this helps.

[flandm]

No faults codes in VAGCOM, no air leaks that I can hear or see (looking for brown staining). Any thoughts on testing the N75 valve.

[pauldazzle]

Could it be the map sensor?

Could be. You can clean it with Isopropal.

[flandm]

Ok so its been to the garage and they have said it is pushing 2grams of air at idle(not sure what that means) and should be about 15grams. Disconnect the MAF and no difference, well apart from the esp light then comes on ? Tried disconnecting MAF myself but absolutely no difference to performance and still no boost. Garage have suggested new MAF required.

[flandm]

Problem resolved, a cheeky little leak in the small bore pipe to the dv.