Audi A3 2.0 TDi (BMN) PD170 Running Issue

[Tricey]

Hi,
I have been experiencing a fault with my car recently, it started when driving home from work, I heard a loud bang, then it started kangerooing until I dropped the revs down. I then progressed to idle home, as soon as i touched the throttle it started kangerooing again. I disconnected the MAF sensor and it seemed to run smoothly but lacked power. I then bought a new MAF sensor and fitted this to find that it had made no difference. I then read about the swirl pot flaps are a commonish fault, I also found that the swirl pot actuator (vacuum) was making a strange noise, upon investigating found that it had a tear in the diaphram I bought a new one of these and fitted it, when fitting this i also cleaned my EGR valve and inlet manifold to remove any carbon deposits that had built up as the flaps where stiff to operate. Once I had done this, I tryed running it again to find I had gained nothing. I have taken it to my local garage and they have diagnosed it to be the MAF sensor. I have tryed a few MAF sensors and this is not seeming to be the problem. There are also no fault codes stored on the system. Any help would be hugely appreciated as this is becoming a large problem for me. Cheers

 

[desertstorm]

I would say that you have a boost leak somewhere. The loud bang was the hose popping and the release of pressure. I would check thoroughly all the boost hoses and the intercooler, boost leaks are usually apparent by the crankcase oil fumes that get blown out resulting on wet oil patches on the hose.
The reason disconnecting the MAF seems to help is the ECU then looks at the MAP sensor to calculate the fuelling. Because the MAF is seeing a lot of air going into the engine but only part of it is getting there because you are losing a load out of the leak.
The amount of boost pressure available is lower and the MAP can see this so the ECU sorts the fuelling. But because you have a sensor disconnected you get a limp home mode.
Is the car mapped or standard?

Karl.

 

[Tricey]

Cheers for the reply, yeah car has been mapped about a year ago and had no running issues until now apart from a new egr valve fitted 6 months ago.

 

[desertstorm]

As it's mapped there is more chance of a hose going or possibly an intercooler failure. I would check this out

 

[Tricey]

Cheers! im on nights this week at work so will get the car over the pit and check over the intercooler and pipes

 

[Tricey]

Found intercooler hose on n/s off. Seemed to re-fit ok and runs perfectly again but loud hissing noise now but doesnt seem to affected how it drives. Cheers for your help Karl

 

[desertstorm]

If the hose has popped off it's liable to do that again, they have metal ears on that wear down and allow it to come off. The seal may be missing damaged which is why it's leaking. You need to sort the leak as this does affect the running.
I would find a garage who know what they are doing if I was you.
You can help intercooler hose joints to stop together with a few tie wraps and jubille clips. New hoses are fairly expensive.