P0171 Vacuum leak HELP

[Fastallroad1337]

Audi a4 2.0tfsi 200hp -2006 with check engine and p0171

Barely not able to remove oil cap when engine is running beacuse of the vacuum in the engine. Replaced pcv and vacuum pump!! What else could be causing this?

I also got an engine knock from the rear of the engine wich i suppose is the cam chain and tensioner, oil pressure is fine, cam follower replaced...

Thanks in advance!

[Theiceman]

vacuum pump has nothing to do with crankcase vacuum. So you could have saved a lot of effort and expense if you had come here first
also high vacuum compared to a 1.8T is normal.
If you have a vacuum gauge check at the dipstick what your vacuum is, im sure someone here can tell you what is normal for the b7. Mine is with my son so i cant check. You want to make sure you aren't chasing ghosts.

Also Crankcase vacuum has little to do with intake vacuum other than they are connected at the PCV. PCV was a good gamble though as usually there is a tear in the diaphragm and it slows unmetered air in.

it is true that the crankcase gasses are pulled in from the crankcase via the PCV. so if you have an RMS leak you can trigger a lean condition. i asume you got a reputable PCV.

so things to check

PCV working correctly.. assume yes as its been replaced.

leak at RMS
leak at intake or anywhere along intake tract
not enough fuel ..

[Jayz691]

What brand PCV ya go with, genuine? A hard to remove cap is a pretty decent indicator of PCV issue. I had a cheap PCV on, for a few weeks(testing reasons), and it failed. No tear in diaphram, check valve from IM was sealing, but it caused crazy suction. To the point it collapsed my silicone lower PCV hose, and was really hard to remove oil cap when running. So they can stick/fail in another way, and cause high vacuum. Far as the lean code, could be a leak anywhere between MAF and IM.

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[Fastallroad1337]

vacuum pump has nothing to do with crankcase vacuum. So you could have saved a lot of effort and expense if you had come here first
also high vacuum compared to a 1.8T is normal.
If you have a vacuum gauge check at the dipstick what your vacuum is, im sure someone here can tell you what is normal for the b7. Mine is with my son so i cant check. You want to make sure you aren't chasing ghosts.

Also Crankcase vacuum has little to do with intake vacuum other than they are connected at the PCV. PCV was a good gamble though as usually there is a tear in the diaphragm and it slows unmetered air in.

it is true that the crankcase gasses are pulled in from the crankcase via the PCV. so if you have an RMS leak you can trigger a lean condition. i asume you got a reputable PCV.

so things to check

PCV working correctly.. assume yes as its been replaced.

leak at RMS
leak at intake or anywhere along intake tract
not enough fuel ..

Vacuum pump was bad so i had to replace it anyway :)

Thanks, ill look at it! :)

[Fastallroad1337]

https://m.autodoc.se/nty/18600950

I bought this one!

Sorry, but What is IM? :)

- - - Updated - - -

What brand PCV ya go with, genuine? A hard to remove cap is a pretty decent indicator of PCV issue. I had a cheap PCV on, for a few weeks(testing reasons), and it failed. No tear in diaphram, check valve from IM was sealing, but it caused crazy suction. To the point it collapsed my silicone lower PCV hose, and was really hard to remove oil cap when running. So they can stick/fail in another way, and cause high vacuum. Far as the lean code, could be a leak anywhere between MAF and IM.

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https://m.autodoc.se/nty/18600950

I bought this one!

Sorry, but What is IM? :)

[Theiceman]

Im = intake manifold

its definitely an aftermarket of some kind, also be sure you ordered the right one for your car. there are two that are almost identical. one has a check valve in it the other doesn't. Not sure it would cause your issue, but just brining it up because we are talking PCVs.

My aftermarket PCV lasted exactly one week.

[Jayz691]

Yeah, that def a cheaper one. I had a cheap Amazon one last about 2 weeks, and caused massive suction. Can't rem if it caused a lean code, but if ya have any small vac leaks, this could make it worse. Id get a genuine PCV before going any further. Check the rear breather pipe. If it has a black end(check valve) you want a "P" revision. If not, "R" revision.

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[Fastallroad1337]

Thanks guys, Will look at it! :)

[Theiceman]

i've seen a bad pcv causing high block vacuum and low oil pressure warnings, but never a vac leak message.

[Jayz691]

i've seen a bad pcv causing high block vacuum and low oil pressure warnings, but never a vac leak message.

No, It won't cause a lean code in itself, if theres no leak.. What I'm saying,, is its possible with a small leak already starting/started, that extra high suction could make it worse. Was just a possibility, but unlikely..

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