PCV is working correctly ?

[BrizZeR]

Hey everyone first post here

I'm a little bit confused about an issue I was having,
I have an Audi 2008 A3 2.0T with 107,000 km on the clock.
Two weeks ago I started having rough idle only on cold morning start ups. the rough idle disappeared after the temp gauge started to move a bit and that's it ,
RPM was normal, but when trying to rev up a little bit the rpm would go up and down (i have a video if that would help) .

I didn't have any check engine light but on one of those cold mornings, I had a fault code detected with OBDELEVEN =P0171 SYSTEM TO LEAN.
So I started diagnosing the issue from that.

the next morning i used OBDELEVEN to check misfire and it did a cycle of 130 misfires most of them came from Cylinder num 4 then 1, cylinder 2 and 3 were pretty ok.
after searching the web i came across PCV valve failure symptoms, i had most of them.

i checked the pcv by removing the oil cap and dipstick (not at the same time) when the engine was running .. i had a suction and a pop sound and the engine went really rough when i removed them ..
from what i saw on the web this is indicating a failure on the PCV ,i also could hear a small whistling noise on those cold starts coming from the little hole on the pcv itself which is also indicating a failure.
i ordered a PCV valve from amazon 06H-103-495-AH and replaced it with my pcv 06H-103-495-A that came out of the factory , and the next morning the issue disappeared! YAY!
just for the heck of it i checked the symptoms again and that's why i think something is strange.
now after the replacement when pulling the dipstick out the idle stays completely the same, correct me if im wrong but this means that the PCV is faulty, if I'm removing the oil cap the engine will go rough until i seal it back .
aside from that i get a better fuel mileage and the issue mentioned above with the misfires has been solved , another thing i noticed which im not sure if it was before is when im removing the oil cap , a white smoke comes out from there , is that normal ?

Thanks in advnace and sorry for the long post

 

[nluk100]

Did you replace the dipstick as these are prone to leaking from the top, which may be why you didn't notice any change. Have your mis-fires gone now?

 

[BrizZeR]

Did you replace the dipstick as these are prone to leaking from the top, which may be why you didn't notice any change. Have your mis-fires gone now?

Hey , thanks for the reply .
No i didnt replaced the dipstick .
Yes the major misfires are gone , i only have like 7 small misfires on cold starts and thats it .
The hard rough misfires i had are gone .
But today i noticed that if i rev up to about 1000rpm i do get misfires for some reason

While im driving i have almost zero

 

[paddy]

"i checked the pcv by removing the oil cap and dipstick (not at the same time) when the engine was running .. i had a suction and a pop sound and the engine went really rough when i removed them ..
from what i saw on the web this is indicating a failure on the PCV "

No the rough idle on the removal of the dipstick or filler cap indicates the PC " is working" if the idle smooths when you replace either

 

[BrizZeR]

"i checked the pcv by removing the oil cap and dipstick (not at the same time) when the engine was running .. i had a suction and a pop sound and the engine went really rough when i removed them ..
from what i saw on the web this is indicating a failure on the PCV "

No the rough idle on the removal of the dipstick or filler cap indicates the PC " is working" if the idle smooths when you replace either

Yes, sorry my mistake
so before that, the idle still went rough when removing the dipstick or filler cap, but now it only goes rough when removing the filler cap ... without the dipstick, it stays the same ..

 

[paddy]

Well your pcv valve is working if it goes rough when you remove the filler. I don't know about the dipstick but over filling with oil might be a problem ?

 

[BrizZeR]

Well your pcv valve is working if it goes rough when you remove the filler. I don't know about the dipstick but over filling with oil might be a problem ?

ok .. over filling isn't the problem .. there isn't any absolute way to check if the PCV is working?

 

[paddy]

with the engine on tickover remove the oil filler and place a piece of paper over the ho9le, it should be sucked against it straight away. If its not the PCV valve is leaking vacuum

 

[BrizZeR]

with the engine on tickover remove the oil filler and place a piece of paper over the ho9le, it should be sucked against it straight away. If its not the PCV valve is leaking vacuum

ok friend il try that tomorrow and update

 

[ch1z64]

Plus check your dipstick is not off the yellow colour and is off the orange colour plus check the Dipstick has its Oring as it doesnt seal correctly without and causes suction . Check all hoses coming from and going too are tight and av a correct seal .

 

[BrizZeR]

with the engine on tickover remove the oil filler and place a piece of paper over the ho9le, it should be sucked against it straight away. If its not the PCV valve is leaking vacuum

Ok sorry for the long delay lol, I checked it today I used a really light tissue and it seems like the engine was sucking it inside .. so that's normal I guess ..
but i still have no change in idle when I remove the dipstick...
i also went to a mechanic to check the PCV and he told me that it is working correctly ..
I'm starting to suspect maybe i have some leak on the dipstick .. i think that what I will check next .. any other ideas?

Plus check your dipstick is not off the yellow colour and is off the orange colour plus check the Dipstick has its Oring as it doesnt seal correctly without and causes suction . Check all hoses coming from and going too are tight and av a correct seal .

It does have the oring on it .. and it seems like it does stuck tight cause i need to apply a bit of force when trying to remove it with the engine on .. maybe somewhere along the tube I have a leak ...



so I will try to make it simple .. currently, the thing that worries me is that when removing the dipstick the idle stays the same...
I also Think that I have less acceleration on low rpm

i have the car for few months so maybe i just got used to the acceleration but I'm pretty sure that i had more power in lower rpm than now

 

[Daveyonthemove]

Check the breather pipe coming off the PCV.
Mine had a hairline crack and was causing a slight misting of oil on the underside of the engine cover.

For me there was no indication of a problem with the PCV as it idled and revved as expected, but the misting of oil concerned me so I checked the pipes and found a tiny crack. £20 for a new one and 5 mins to replace.

 

[BrizZeR]

Check the breather pipe coming off the PCV.
Mine had a hairline crack and was causing a slight misting of oil on the underside of the engine cover.

For me there was no indication of a problem with the PCV as it idled and revved as expected, but the misting of oil concerned me so I checked the pipes and found a tiny crack. £20 for a new one and 5 mins to replace.

any way to test if the pipe is broken?
and what do you mean by misting?
you talking about opening the oil filler and smoke coming out?

 

[Daveyonthemove]

No, I never mentioned the oil filler or smoke.
On the underside and front edge of the engine cover I found a small amount of oil, as if it had been sprayed like a water mister.
If you have any oil on the cover or breather pipe, there is a chance it has a split in it. If you don't have any oil anywhere, then it's probably fine.

 

[BrizZeR]

No, I never mentioned the oil filler or smoke.
On the underside and front edge of the engine cover I found a small amount of oil, as if it had been sprayed like a water mister.
If you have any oil on the cover or breather pipe, there is a chance it has a split in it. If you don't have any oil anywhere, then it's probably fine.

sorry, i wasn't focused haha i was talking about the mist you mentioned, i will check that too .. thanks!

 

[Whodafunk]

Removing the dipstick or oil filler cap creates a vacuum leak. Similarly, if either aren’t sealing or leaking slightly this will also create a vacuum leak. These vac leaks are adapted by the ECU overtime (evident in the long term and short term fuel trims LTFT / STFT). The ECU can only make alterations upto around 20% plus or minus, in order to effectively achieve Stoichiometry, or lambda.

What I’m saying here is given your pre existing lean fault, you may have a leak on the dipstick which once outside of the ECUs parameters is creating a fault code and the poor idle.

The issues under load are less likely to be vacuum related as vac leaks are only really apparent at idle, so these are more likely to be linked to your misfire issues.

If you have access to VCDS, with the engine running and upto temperature (so it’s not running in closed loop), look at measuring blocks 032 and 033 for LTFT and STFT. Watch the idle value change in the short term trim when you remove the dipstick as this creates a vacuum leak. Your long term trim should show a figure over 20% outside of range indicating an adaptation made to correct the vacuum leak, providing no fault codes have been cleared recently.

 

[BrizZeR]

Removing the dipstick or oil filler cap creates a vacuum leak. Similarly, if either aren’t sealing or leaking slightly this will also create a vacuum leak. These vac leaks are adapted by the ECU overtime (evident in the long term and short term fuel trims LTFT / STFT). The ECU can only make alterations upto around 20% plus or minus, in order to effectively achieve Stoichiometry, or lambda.

What I’m saying here is given your pre existing lean fault, you may have a leak on the dipstick which once outside of the ECUs parameters is creating a fault code and the poor idle.

The issues under load are less likely to be vacuum related as vac leaks are only really apparent at idle, so these are more likely to be linked to your misfire issues.

If you have access to VCDS, with the engine running and upto temperature (so it’s not running in closed loop), look at measuring blocks 032 and 033 for LTFT and STFT. Watch the idle value change in the short term trim when you remove the dipstick as this creates a vacuum leak. Your long term trim should show a figure over 20% outside of range indicating an adaptation made to correct the vacuum leak, providing no fault codes have been cleared recently.

Hey, thank you for your message and explanation let me try to explain again
The Lean fault and misfires have been solved by replacing the PCV ..so I don't have that issue anymore .. the only thing that bothers me is that when im removing the dipstick .. the idle stays the same as in this video...


so that's why im confused .. the mechanic checked the PCV and said that it is working fine..
Only thing i can think of is that i have a leak on the dipstick which is getting adapted overtime .. so when im pulling the dipstick it doesn't change anything cause there already a leak ..

I also had "oil burned" since the PCV failure and it seems like also after replacing it .. im still checking it as i didn't put a lot of mileage in those past few weeks

 

[Whodafunk]

Was the gasket changed when the pcv valve was replaced? I wouldn’t rule out a faulty new pcv valve. I think I have something similar. Replaced my pcv and gasket with a new genuine audi part (not cause it was faulty but more as a preventative service part) and now I’m getting a little oil mist on top of the pcv valve and a smell of oil vapour when warm. Could be a break to one of the breather hoses which I’m currently investigating, if not I’ll be putting the old pcv valve back on.

You may also have a slight leak to a breather perhaps

 

[Whodafunk]

I’ll remove my dipstick while the engine is running and see what it does for comparison.

 

[BrizZeR]

Was the gasket changed when the pcv valve was replaced? I wouldn’t rule out a faulty new pcv valve. I think I have something similar. Replaced my pcv and gasket with a new genuine audi part (not cause it was faulty but more as a preventative service part) and now I’m getting a little oil mist on top of the pcv valve and a smell of oil vapour when warm. Could be a break to one of the breather hoses which I’m currently investigating, if not I’ll be putting the old pcv valve back on.

You may also have a slight leak to a breather perhaps

no, I didn't replace the gasket and you mean removing the dipstick completely?

I think I will check the car this weekend for any leaks... if I don't see anything I will just wait until the next service in about 1000-2000 km and nudge the mechanic about it lol .. I just hope it won't be the PCV cause I can send it back to Amazon only for the next few days

 

[Whodafunk]

I mean just pull it out slightly not completely remove.

I’d get the gasket changed. If I remember correctly it’s £20 ish from audi

 

[BrizZeR]

I mean just pull it out slightly not completely remove.

I’d get the gasket changed. If I remember correctly it’s £20 ish from audi

while the engine is running?

and i will do it in the next service or maybe if i get the chance any time soon

 

[Whodafunk]

Yes, whilst it’s running. I mean as in the video you posted. I’ll do it with my car to see if it does anything different

 

[BrizZeR]

Yes, whilst it’s running. I mean as in the video you posted. I’ll do it with my car to see if it does anything different

yes that will be really helpful thanks!
and that's what im doing .. same as in the video .. removing the dipstick