Help needed in solving this mystery of p0101,p0420,p0299

[B44]

It all started like this. I see a empty street pull out of the parking and i slam the gas as the boost was building up suddenly the car makes a sound THUD and the esp light, parking malfunction and cel light up. Now i assumed some hose poped off so i drive to the garage lift the car to check if the vaccum hose on the forge dv poped or not. All was ok bought a vagcomm scanned got the above codes. First thought the n75 was busted repalced it no luck. Now car is in limp mode. And inside the car the turbo sounds weird uploading a video hope its clear. Any help will be appreciated.

Following are codes description
P0101 mass airflow
P0420 cat below effcoency
P0299 turbocharger under boost

http://vid1375.photobucket.com/album...pshh0cvfj7.mp4

[DoctorB8]

sounds like a wastegate flapper. looks like new turbo time. either can get a used ko3 or upgrade

[B44]

Does the b8's have secondary air injection pump?

[van462]

I think you have a boost hose popped off. the MAF is reading all this air getting pumped by the turbo, the ecu is setting the fuel mix based on that air amount. 420 code likely as you will be running very rich. 299 code because MAP sensor isn't seeing the boost come up.

[B44]

I checked all the hose from top of the engine are there any hoses underneath the turbo i need to check?

[B44]

Also what i did was i cleared the codes and the mil and started the car the car died off again i started it it was dieng so i gave some gas and rev it and the lights turned back on.

[van462]

The connections from the turbo outlet to the intercooler and then all the way to the intake manifold. You can pop out the fog light grills to check the intercooler connections.

[B44]

I have the ecode billet ic pipes dont think they would pop off.

[Alex1188]

I have the ecode billet ic pipes dont think they would pop off.

check all pipe connections, just cuz you have piping and not hoses doesnt mean the silcone connection didnt come loose...

[B44]

alright will do check again.

[B44]

Ok check the pipes nothing loose any other advice?

[van462]

Try starting and letting it idle with the MAF unplugged. Without a signal it it should at least idle. It will also won't allow significant boost to build. ( I just went out and tried it on my car to be sure). If you idle returns normal then I'd get a MAF. Next I'd disconnect the hose from the intake manifold and do a boost leak check from the the turbo to the intake.

If all that passed I'd slide the cat back a few inches and do a quick check on the cell structure in the cat and since the turbine wheel is right there check for shaft play and see if the wastegate is tight.

[B44]

Alright i did check the wastegate by moving thr rod for play dint feel anything. The maf sensor is just non responsive idle is same. Also like how when then car is cold and you start and it idles higher for 2 mins it does not do that. So i am thinking does our car have secondary air pump like older models and may be thats faulty? Anyways Now i will try the other things which you recommended. Anyways a big thanks to all you guys for the advice. Also quick question can my forge dv be the cause or the solenoid that directs vaccum to the dv might be faulty. The sound comes from the bresther pipe area down towards the turbo outlet.

[UmIsThisThingOn]

P0299 turbocharger under boost

That is the dead giveaway that your turbo's wastegate is flapping and you'll need to have the turbo replaced.
I just went through this.

[van462]

A 299 by itself I would agree, tied with the other codes not as clear cut. Code p0101 indicates massive air leak on intake. Invalid maf signal will kill boost to protect the motor. Plus he said the wastegate actuator rod was tight. That hopefully means the wastegate has enough tension to keep the flapper seated.

I haven't troubleshot with a forge dv. If it stuck open it would act as a vacuum leak at idle and air would enter without being metered by the maf. As turbo speed comes up it would reverse flow and become a boost leak. Being that it vents to atmosphere vs being recirculated it would cause bigger issues.
The dv is near the turbo outlet. Do another visual on the outlet adapter and piping. Start the car and listen for leaks, maybe spray some WD 40 around the dv and listen. If its getting sucked in you will usually hear the engine change rpm some. If you have your stock dv still swap it back in for a bit.

[Alex1188]

did you have the forge dv installed and ran before all this happend? if not i would check the hose routing to the solenoid that controlls the forge dv, if hooked up backwards, could cause the dv to be opened when boost trys to build. But the thud sound to me sounds like, a IC connection coming off or loose, seeing how this has happend to me before with my CTS kit which has metal piping as well.

[B44]

I had the forge dv 7k miles ago with no issues. Now only thing is I have to check the ic pipe I don't have the stock dv as it broke so ill try the wd 40 method to check the dv.

[B44]

Ok I check the ic pipes and the dv with wd 40. Nothing. So now ii cleared the codes and then try to start the car it died right away. Now only question is this due to bad dv or the turbo if I rev the engine when it tries to die it right away goes in limp mode and idle becomes stable. Uploading a video if that can help.

[B44]

http://vid1375.photobucket.com/album...psml4ztcn4.mp4

[van462]

If the piping is all good and idles with the MAF unplugged; then I would think the MAF is the culprit. But a bad MAF won't cause any odd sounds. Only other place I can say to look is under the engine cover and make sure the hose from the oil seperator/PCV is connected. Maybe even disconnect the hose from the intake manifold and temporarily block it off (plastic bag and a zip tie will work). One more way to eliminate a leak on intake.
I can't see the turbo itself being a factor with low idle and maf readings. Unless it had a major failure to where the impeller somehow is jammed. At idle is just spinning but no real compressor effect. Not sure I can be of anymore help.

[DoctorB8]

Did you recently tune the car?

[B44]

No have all mods and tune from a year now. This just happened out of nowhere. And it's not the maf replaced it with another one

[DoctorB8]

When you originally had a tune did you bench or port flash it

[B44]

My dear audiziners you all have been very helpful and I appreciate all helping me out truly. The problem has been solved the ic pipe on drivers side popped of in such a way that you could only know it's loose if you wiggle check it. I apologize for not doing that before. All is good now car drives great.

What I learn from this
1.check maf
2.check all vaccum lines and dv
3.check ic piping
4.check connection between intake and pcv
5.check for bad n75 valve.

These can be the top most things to look for the codes above. Before jumping to conclusion of bad turbo or bad wastegate.

[Alex1188]

My dear audiziners you all have been very helpful and I appreciate all helping me out truly. The problem has been solved the ic pipe on drivers side popped of in such a way that you could only know it's loose if you wiggle check it. I apologize for not doing that before. All is good now car drives great.

What I learn from this
1.check maf
2.check all vaccum lines and dv
3.check ic piping
4.check connection between intake and pcv
5.check for bad n75 valve.

These can be the top most things to look for the codes above. Before jumping to conclusion of bad turbo or bad wastegate.

Glad to hear you got it figured out! I knew once you said thud sound and lost all power it had to be an intercooler hose.

[B44]

Thanks a ton Alex for the ic check.