A4 b6 1.8t avj 2002

[Jay 18t b6]

Wondering if anybody can help me out here so I drive the b6 A4 1.8t had it for some years now late last summer I noticed a problem when I was on full throttle (any gear) mostly noticed in 3rd gear when applying full throttle the car seem to be surging like it was giving full power then letting off then giving full power again then letting off and this was with throttle fully open. No check engine lights on the dash no other symptoms. Then the cam chain tensioner failed and I had it replaced just the tensioner not the chain all was timed back up and running again but now I have a check engine light for p0171 and I have little to no boost or power.so I've cleared the code and took it for a run and the powers there again for a few minutes then it goes back too the lack of power and eventually the check engine light comes back on again. So far I've looked and listed for vacuum leaks I've changed the n75 valve for a new one, I found one split hose replaced that with one from an auto shop found another that didn't look great witch was connected to the crankshaft breather hose witch was also smashed so replaced that too I'm just stumped as to what it could be, I was thinking maybe the waste gate was at fault but after the code is clear you get a few goes at full throttle and all the power is back but then goes back into what I'm guessing is limp mode anybody have clue what could be causing this ?

[TobiqueSlang]

Are you sure you retimed the cams correctly when you replaced the tensioner?

Otherwise a lean code could be cause by any number of things beyond just a vacuum leak.

[Jay 18t b6]

Yeah as far as ino the cams went back correctly because the first time we put it all back together it was running rough when idling and also it was struggling to start unless you had the throttle fully open so we took it all back apart and the cams was slightly off then when we put it all back together all the markings and chain was correct after counting it and it started up straight away without holding throttle open and we turned it off timed it up again just to check and it was all still lined up correctly

[TobiqueSlang]

If the timing is good and you've got the vacuum system sorted then you're looking at a bad/dirty MAF sensor or a fueling issue which could be the pump, the filter or bad injectors. but even then it could still be a number of things.

[Jay 18t b6]

So I've cleaned the MAF 2 weeks ago refitted and cleared code and had the same result power was back for a little bit then lost power then check engine light came back on its so strange because if I clear the code I have full power back for a few bursts but u can still feel it holding back then it's gives full power then holds back again wouldn't I get other codes for fuel pump bad injectors ? The only code that comes up is p0171 bank 1 too lean I think that's what it said

[TobiqueSlang]

So I've cleaned the MAF 2 weeks ago refitted and cleared code and had the same result power was back for a little bit then lost power then check engine light came back on its so strange because if I clear the code I have full power back for a few bursts but u can still feel it holding back then it's gives full power then holds back again wouldn't I get other codes for fuel pump bad injectors ? The only code that comes up is p0171 bank 1 too lean I think that's what it said

It could be a bad O2 sensor. when you clear a DTC from the system and the car runs better it could be a case of the ECM no longer having long term data to work with, so essentially you're working with a clean slate temporarily until it has a chance to notice something is wrong.

are you just using a regular OBD2 code reader? A regular code reader will only give you generic DTC information, in order to get anything more specific you'd need to use VCDS/VAG/OBD11

Basically all a P0171 will tell you is that you've either got too much air or not enough fuel.

[Jay 18t b6]

Ive read it on two different types of code readers one is the standard red obd2 reader and I've used and expensive one from a Merc break down specialist his one can give me live data but I don't know what I'm looking at with it and they both give the same code p0171 bank one too lean

[Jay 18t b6]

Anybody else have any suggestions or help

[Nirvana09]

When I first bought my audi about three years ago I had weird surging issues KIND OF like what you're describing. If I remember correctly it was a cracked side mount intercooler - it would open, the cool air would close the crack, it would heat up and open again ect ect. I upgraded to a front mount intercooler and never looked back. I would check for a small leak somewhere in the intake system. Going to the hardware store and making a pressure tester with PVC components/tire valve/PSI gauge will let you find the leak near immediately.

[Jay 18t b6]

I'm going to try and make a smoke machine and test for leaks