Lack of boost...could it be the turbos???

[Tweaky]

Hi all

I have just come back from a trip to France in the car. On the way back i noticed a definite lack of boost/power for the car. When i got home i removed the diverter valves and checked them, but they are both fine. I had the car serviced about 3000 miles ago, and while it was in i had the DV's replaced along with the 'F' pipe and the TBB. These pipes still look in fine condition, although i haven't removed them. I am not getting any smoke from the exhaust and the turbos seem no louder than they where before, so i am at a bit of a loss as to what is causing the problem.

Any ideas?

[DavidR]

My S4 is allergic to France too, having suffered a faulty DV and a torn TBB (fortunately I had spares in the boot for a middle of nowhere roadside repair)...


However, back to the point, I had a very similar problem to what you describe when the air mass meter became faulty. Initially a loss of boost to 0.6bar but no error codes on the car, then both banks running lean error codes and 0.3bar (on a stock map)

It would therefore be wise (DTCs or not) to consider a temporary swap of air mass meter (with ECU reset in between) and logging the boost.

I guess there are many other potential causes too, but my local specialist blames air mass meters 1st then DVs, TBBs, then loose / broken hoses elswhere on the pressure induction side...

My experiences with Audi dealers with these problems are that the claim the car to be fine so long as no error codes are logged. AmD will get to the bottom of it if it proves tricky though.[/img]

[Dippy]

I had low oil level in France. Maybe there's a pattern here...

Tweaky, do you have access to VAG-COM to check for codes?

[Nige_RS4]

As DaveR suggests, try swapping your MAF (I've heard Audi are doing an exchange for £80 or so at the moment, but I've not had any confirmation of this?). If you do reset the ECU, make sure you clear the fault codes and carry out a TBA (throttle body adaption).

I would check for any specific fault codes, but it could still be your MAF, as mine went AWOL without any fault codes being generated?!*!

Also beg, borrow or steal a boost gauge to see if you're going into limp mode.

Nige.

[Tweaky]

I think you are probably right about the MAF as it seems to be intermitent. some times when i start the car all is fine, but other times it has no boost. It is booked in to be checked out in a couple of weeks time, so i will have to just wait and see what happens.

[Dippy]

I agree with Nige about a boost gauge, it really helps you to know what's going on. I had limp mode once and the ECU held the boost at 0.4 bar maximum, no variation whatsover. Other problems (such as air leaks) would have cause a variation.

[KayGee]

I would definetly do a vag-com test to see if any DTC are listed (no location listed so can't see if I can help here). Also a log of g/s airflow should show if the MAF is at fault. If you can find an owner with vag-com and the same Maf an hour or so should cover the time required to do a comparison run and swap MAF sensors (includes discussion over a cup of tea and compliments of each others cars...).