# P0101 and p0171 has my VW specialist scratching their heads



## Dubveiser (Aug 4, 2005)

*P0101 and p0171 has my VW specialist scratching their heads *edit, worse now**

I've had a p0101 code for almost four weeks now. My car is a bone stock 2008 2.5L. Only mod is a Neuspeed intake that I've had for three years problem free.

Last month I got a check engine light after replacing my cone filter. I scan the ecu and a p0101 (MAF implausible signal) pops up. I figured the oil from the new filter contaminated the MAF sensor. These are the steps I've taken so far to solve the issue.

1. Clean the MAF - check engine still on
2. Replace the MAF with a new unit - check engine still on

At this point, I take it to an indie VW shop. They detect a leak in the flex pipe, which could throw a p0101 since it's before the rear 02 sensor.

3. Repair leaky downpipe - they return the car, and the car throws a p0101 less than an hour later

4. Take it back again. They do a smoke test, detect a leak in the secondary air o-ring on the intake. Fix the leak, they do another smoke test, no leaks this time. 

I get the car back, runs fine for a bit, then 15 minutes later, I get a check engine. P0101 again, this time I also get a P0171 (bank 1 too lean)

The garage said they don't know what to do aside from randomly throw parts at the car and see what fixes the issue. I'm at a loss. Don't know what to do and where to start. My garage doesn't know either.

Anyone have any ideas?

To resume I've done the following
- new MAF
- checked MAF wiring up to ecu, everything is fine
- smoke test - no intake leaks
- no exhaust leaks
- MAF readings on vag-com are within specs when you clear the codes and drive normally. Once you do a WOT run, codes come on and loses power and has poor fuel economy ...

What am I missing?


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## le0n (Jun 12, 2013)

you changed the cone filter.

was it the exact same filter brand/design? if not, this could be your problem.

put your old one back on and see if the code vanishes.


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## Dubveiser (Aug 4, 2005)

Put the old filter back on.

Same story.

Now it's worse. Last night I got an array of codes after a cold start. P0300, P0301, P0303, P0304, P0305. No check engine though.

Erased the codes, still getting P0101 and P0107 within a minute or two of driving.

My MK5 has turned from the most reliable car I've ever owned, to a complete disaster with all these random codes.

I pulled the plugs today, they are mint. The VC gasket seems a tiny bit leaky, but nothing serious.


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## le0n (Jun 12, 2013)

random misfire P0300, plus the other misfires makes me believe it is a vacuum leak.

failed N80 purge valve will give you a vacuum leak. it's cheap.

you can clamp the hose shut (vise grips with two pieces of wood (to protect the hose)) to see if the error code goes away.

you may get a code for the evap system though, however, it will tell you if you N80 is stuck in the 'open' position.

edit: the P0107 is new. perhaps you should take a look at the P0106 thread that's here: http://forums.vwvortex.com/showthread.php?5626102-Picking-your-brain-again-vortexers-09-Rabbit-P0106-P2178-P2188
(the meaningful information starts on the second page).


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## Dubveiser (Aug 4, 2005)

le0n said:


> random misfire P0300, plus the other misfires makes me believe it is a vacuum leak.
> 
> failed N80 purge valve will give you a vacuum leak. it's cheap.
> 
> ...


My bad, it's still P0171, I made a typo on my second post. Thanks for the leads! Will look into it.


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## le0n (Jun 12, 2013)

oh, hah hah.


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## Dubveiser (Aug 4, 2005)

*Update*

Brought it to another VW specialist.

He noticed excessive vacuum in the motor (oil cap was impossible to remove while the engine is running). He was convinced this was causing the P0101, P0170. He replaced the PCV valve, and the VC gasket.

Five minutes later, guess what, P0170 and P0101. The icing on the cake, there's ANOTHER new code. P2279. This car is cursed. I get that we haven't yet found the source of the problem, but it's strange that the car throws NEW codes only when it leaves the garage.

I'm dumping this POS... It served me well for years, but I don't have time to deal with the issues...


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## le0n (Jun 12, 2013)

Dubveiser said:


> I'm dumping this POS... It served me well for years, but I don't have time to deal with the issues...


i believe your VW Specialists are incompetent when it comes to this platform. perhaps they are specialist with the MKIV platform? you're relying on them to do the correct thing and wasting time and money. a trip to the dealership would have served you well in this case because they have the right tools and know how to properly diagnose the error codes you are getting.

did they show you the torn diaphragm from the PCV when they removed it? did they replace it with a Doorman diaphragm vs. the entire valve cover assembly? if so, it could have been improperly installed. give us a little more information on what parts were used.

also, in the future (with this car or the next) don't rely on smoke test results.



le0n said:


> failed N80 purge valve will give you a vacuum leak. it's cheap.


have you ignored this bit of information? i didn't see a response to this suggestion.


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## Dubveiser (Aug 4, 2005)

le0n said:


> i believe your VW Specialists are incompetent when it comes to this platform. perhaps they are specialist with the MKIV platform? you're relying on them to do the correct thing and wasting time and money. a trip to the dealership would have served you well in this case because they have the right tools and know how to properly diagnose the error codes you are getting.
> 
> did they show you the torn diaphragm from the PCV when they removed it? did they replace it with a Doorman diaphragm vs. the entire valve cover assembly? if so, it could have been improperly installed. give us a little more information on what parts were used.
> 
> ...


My mechanic is a Vw-audi specialist that my family has been loyal to since the 80's. He really does top notch work, I trust him fully, and he's about as pissed about the situation as I am. 

To be fair, my car has been running better since the PCV valve replacement. And everything they've fixed so far HAD to be fixed. There was no doubt the PCV was torn. I could hear the whistling when I shut off the car and it was impossible to remove the oil cap while the motor was running. My car also did have an exhaust leak that I had to fix either way. I'm just very disappointed that the codes are still there. 

He didn't cut any corners doing the job, he installed a new valve cover, valve cover gasket, PCV valve and PCV hose. All oem parts. The MAF readings are correct, he did a throttle body alignment, didn't detect any intake leaks.

He said next step would be to re-install the stock air box back on, and have him drive the car home a day or two and go from there. He's probably right. I only tested the stock air box on for an hour or so, and that was before the PCV replacement.

The p2279 is gone now. I took it back, there was an intake hose that wasn't properly snapped back in, the billet aluminum inserts on the Neuspeed p-flo require much more pressure to clip on compared to the stock intake.

But still, whole situation is a mess. Could it be that my car suddenly doesn't like my p-flo after many years without issues?


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## le0n (Jun 12, 2013)

^^ sounds like he did what he needed to do. it's just nice to know upfront if we're trying to figure things out on this side.

i'm not sure how the p-flo was designed. was it one of the setups that needed a MAF insert to prevent the CEL? i know a lot of them needed the MAF insert/baffle to run code free. some people got lucky and didn't need them. i'm not sure if it was from the environment they were in or a certain coding they had in the ECU.

but yes. you should be definitely diagnosing with the stock airbox on.


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