code P0171

[dmode951]

So I have a check engine light on and I pull up this code P0171.

So I'm getting all kinds of different feed back on what it might be.
I'm loosing power on take off and she seems sluggish, so I'm thinking a vacuum leak.
But I'm also hearing O2 sensor, fuel injectors, intake leak.

So can anybody clarify on what I should really focus on first.

And does anybody know if I can do a smoke test on the vacuum system for leaks and a good place for it.
Yes I'm new to Audi and learning as I go.

Thank you

[Jhb5]

Check for spark, check fuel pressure, check all of your injectors. Check coils.


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[dmode951]

I have spark, Coils are new, going to clean injector this weekend and check for wear.
I don't have a fuel pressure gauge

[FeebleBiscuit]

Well starting with the vacuum system is never a bad idea it’s the cheapest and easiest. It probably need to be gone through either way. But for the others do you have vagcom?


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[dmode951]

I just have the Blue Driver OBD scanner.

If I do a smoke test what hose do you recommend I use for my machine ?

I ask because Audi's are a lot different than most cars. Same Idea different set up.

[FeebleBiscuit]

I just have the Blue Driver OBD scanner.

Well that’s cool but the next spare 200 bucks you have I would pick up a vagcom cable. You can buy the eBay one but it’s nice to just have the plug and play of a genuine cable. It can really help test sensors because for all you know it could be a bad MAF. My a4 and my s4 both have had MAFs go out of spec. I never got a code but the car ran like crap under full throttle. With the cable you can pull up the MAF sensor and see that it’s not reading enough air. I also got the lean code when I had a bad MAF and the car was in limp mode.



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[FeebleBiscuit]

Do you have a fmic? You can probably inspect all the boots and see if there any leaks. 5 years of owning these cars and I have never actually needed a smoke tester.


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[MacFady]

Well that’s cool but the next spare 200 bucks you have I would pick up a vagcom cable... for all you know it could be a bad MAF.

5 years of owning these cars and I have never actually needed a smoke tester.

10yrs of owning these cars and I've never needed a VAGcom cable. You can read MAF values with most, if not all, generic OBD apps like Torque.

[FeebleBiscuit]

10yrs of owning these cars and I've never needed a VAGcom cable. You can read MAF values with most, if not all, generic OBD apps like Torque.

Ha well if want to make it more difficult for yourself for fun, go for it. I bet your car sits in the garage a lot.


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[dmode951]

10yrs of owning these cars and I've never needed a VAGcom cable. You can read MAF values with most, if not all, generic OBD apps like Torque.

I can get the cable. My friend has a spare one I can have.
It seems I can download the software of Ross-tech I just need to know what version.

The MAF I have the cleaner for it i can try and spray some to see what happens. If no change I'll just by another one just to make sure and rule it out.

And as far as the smoke test I do it to all my cars once in awhile just to make sure everything is sealed.

[MacFady]

If you already have the smoke tester just go for it. As someone else said, while more difficult to track down (perhaps not for you) it is generally a cheaper fix. What are your boost and vacuum readings in real time, does your OBD dongle let you view those things in real time?

[dmode951]

Yes, It saves it to my phone.

[FeebleBiscuit]

Check this out.

https://www.audizine.com/forum/showt...ror-BACK-AGAIN!!


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[dmode951]

Thanks for the link it was a good read.
I will work on it.
First I'll check MAF if that doesn't work I'll go to vacuum lines If nothing then the N80.
Process of elimination right.