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So I just bought a 2006 Audi A4 TDI. My very first Audi and it wouldn’t be long until I noticed that this car has a mind of it’s own. Every time I go WOT (wide open throtle) upphill it cuts out.
The previous owner had the same problem and he had the car at various workshops but none of them managed to fix the problem.
What happens is that when I put down the gas pedal going uphill it will accelrate for a few seconds, then I loose all power as the car goes into “limp mode”. If I cycle the ignition off and on again it’s back to normal, as long as I don’t floor it again.. This only happens going uphill! I can floor it going stright in every gear, no problem, it’s just going uphill!
I got my hands on a laptop and a vagcom cable and red the stored fault code. It sais: Overboost condition – intermitent.
The car is fully oem. I’ve googled this and I see that many has the same problem with the car cutting out due to “overboost condition”, but noone seems to have the exact same problem that I’m having, with me it’s just going uphill, which is kind of weird because the engine is under 100% load with max boost going stright also, so why will it cut out only going uphill?
The things I’ve searched and found as possble faults is:
Vacuum leak
N75 valve (regulating vacuum to the turbo actuator)
Variable vanes inside turbo stuck
AFMBut none of this makes any sence with my problem. If there was a turbo regulating issue, why does it only happen uphill and not when I floor it going stright? The turbo spools up and the car produces power just fine!
If it was a vacuum leak, still, I should think it would happen more often, not just uphill?It’s just every time i go uphill this happends.. and that sadly is every day, because I have to travel trough an undersea tunnel with a 7% incline uphill :unsure:
I can avoid it by not pushing the pedal down fully, not allowing the turbo to peak boost. This is the newest car I’ve ever had and I’ve been saving up for a long time to get it. So this problem is not any fun at all :unsure:
Has anyone ever heared of something like this?
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I take it the code you got was p0234? The turbo is over
boosting and the car is going into limp mode to save the
motor.when you cycle the key your resetting the problem.
why this happens on a hill only.That I can’t answer.If I’m
honest.You may have stuck/dirty turbo vanes.http://www.youtube.com/watch?v=uK9dFNS-ddM
http://www.myturbodiesel.com/1000q/a4/VNT-wastegate-adjust.htm
That is an interesting problem and I think College man might be onto something. One thing that came to my mind was a fuel delivery issue. When going uphill and accelerating the fuel moves to the back of the tank. At that time if things aren’t positioned in the tank correctly, or the baffles have come loose, this will starve the pump for fuel. It’s a long shot I know but if you don’t get any traction with the College man theory you might look into that possibility. To be honest I’m not sure why that condition would set an over boost code either. It’s just a thought I had based on your description.
Keep us posted on your progress.
I did what the video told me. But I imediately noticed that in my case the rod is able to move all the way, there is no sticking in my case. I still used a long screwdriver pushing it up just to be sure, but when I enabled and disabled vacuum to the actuator it moved all the way, so It must be something else causing it. :
I thought about a fuel issue too, but I just can’t get my head arround why it would throw a overboost code.. It don’t make any sense.. 🙁
Thanks again!
I’ve been reding and reading. This is heavy stuff. Seems there is allot of stuff that can cause this, and allot of possible causes. I feel like I’m studdying for an exam, there’s just so much to get into and understand in order to properly diagnose this issue.
Anyways, After reading for hours, I think in my case the most likely scanario is a vacuum leak, causing the actuator rod to move to slow, causing the ecu to trigger limp mode. I’ve watched videos of the actuator moving, and allthough mine has perfect travel, it do seem to move a little slower than the ones I’ve seen on youtube.
I have ordered a vacuum tester from ebay, I see the rod should move to the fully extended position at 18 hg, but that 25 hg is what’s “normal” for the engine to produce.
I will attach my test instrument in between the line to the actuator itself, to confirm that the vacuum is as it should.
If it’s not, I foundn this: http://www.youtube.com/watch?v=9CPqbaSgcok
But all my vacuum lines are covered with some plastic wrapping, so I don’t think this technique will work on this car. Any other way to find a potential leaks?
I was thinking of hooking up my air compressor, aplying pressure and listening for leaks with the engine off, but several one way valves would probably make that difficult. unless I check at many different locations. `?
I would not use compressed air. you may damage more than do good.
Eric’s method will work even with wrapped lines.You could use a spray
bottle with water and spray the lines or get a cigar and try this method.You can also use water in a spray bottle instead of carburetor cleaner. Vacuum leaks on a turbo engine are a bit different however. Instead of vacuum in the intake you sometimes have pressure which can make finding leaks difficult. You might also try looking up the troubleshooting for the code you have.
Eric:
I was looking to understand how the wastegate actuator works on theese cars, compared to ordinary petrol cars where there is a spring loaded wastegate that opens at a given pressure (this is a tdi). On this car it seems to be the other way arround, the way I have understood it then the spring keeps the wastegate / variable wanes closed and when vacuum is aplied trough the n95 valve (solenoid) it opens. So it opens on vacuum and not by positive pressure.
There is a vacuum reservior, and I think there is a vacuum pump as well somewhere, but I havent found it yet.
But if there is a vacuum pump that operates this system, then theese methods won’t work since the air isn’t ending up in the engine right? So how can I troubleshoot it then?
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