Hi folks, 

 

I would be grateful if anybody could help me with excessive engine vacuum in my 2008 2.0 TFSI VRS with 190,000 miles (Ive had it since 3 years old).

I first became aware of an issue when it threw up the CEL, code P0171 - lean burn bank 1.  The car drives perfectly, pulls very well etc, idles normally, no blue smoke or excess oil consumption.

I checked for vacuum leaks and found a split hose at the brake vacuum pump which I have now sorted. There are no leaks remaining.

Problem is that there remains to be HUGE vacuum on the engine. It is impossible to remove the oil filler cap while the engine is running. To be able to remove it I have to break the vacuum by removing the dipstick and then struggle with 2 hands to remove the filler cap. Also  since repairing the vacuum leak when I switch the engine off I can hear oil gurgling from within the engine which occurs until the vacuum is dissipated. I replaced the PCV valve in the hope of resolving the vacuum issue, even though the existing valve appeared to be working normally. 

 

Does anybody know why i could have such a huge vacuum? I'm concerned that oil may be vacuuming to where it should not be and hence the gurgling!

 

Many thanks

Don't know a lot about that engine, to put it mildly, including whether this is an appropriate page from the parts catalogue, but if it is, can you tell me what hoses 4 and 15 connect to at the ends not shown near anything?

https://skoda.7zap.com/en/cz/octavia/oct/2007-419/1/103-103090/#15

 

 

From what I understand hose 4 goes to the intake manifold, that is where the vacuum originates from at idle. Hose 15 is the rear breather hose which joins in just before the turbo which is where the vacuum comes from when under boost. My issue always occurs at idle

Make sure that hose 15 and its connections aren't blocked?

Op. No experience of this issue here, but as you say, it has to be coming from intake manifold and that means faulty pcv doesn't it?

 

https://www.golfmkv.com/forums/index.php?threads/high-crank-case-vacuum.147042/

 

Did you replace the pcv with a new, genuine part?

 

12 hours ago, TheClient said:

Op. No experience of this issue here, but as you say, it has to be coming from intake manifold and that means faulty pcv doesn't it?

 

https://www.golfmkv.com/forums/index.php?threads/high-crank-case-vacuum.147042/

 

Did you replace the pcv with a new, genuine part?

 

So i replaced the original PCV, which had a torn diaphragm, about 2 years ago. The replacement was an aftermarket one, then I replaced that again last week with a febi bilstein one. I've ordered a vacuum tester and if that shows a high value then I will order up a genuine PCV valve as it must be that which is causing the excess vacuum.

You can generally pop the lid off the diaphragm-holding part of the PCV valve, by releasing a bunch of plastic 'ramp clips' around the perimeter. Go gently as you don't want to break the clips but that would allow you to visually inspect the diaphragm for tears. 

 

On the engines I'm more familiar with there is a filtered atmospheric pressure air feed into the crankcase (a narrow pipe from air filter to cam cover) which helps to flush through the crankcase gases. If this feed were blocked up, and the engine has minimal blow-by, it could be that the PCV is working correctly, but there is no 'replenishment air' to replace what is being sucked out at idle.  That's why I was suggesting that you check that the pathway involving pipe 15 is flowing OK.

13 hours ago, lloydy123 said:

So i replaced the original PCV, which had a torn diaphragm, about 2 years ago. The replacement was an aftermarket one, then I replaced that again last week with a febi bilstein one. I've ordered a vacuum tester and if that shows a high value then I will order up a genuine PCV valve as it must be that which is causing the excess vacuum.

Yes. the vacuum present should be no where near as high as manifold vacuum at idle. I tried measuring vacuum with a normal engine vac gauge on my EA888 engine and couldn't get any reading.   I was told the pcv vac at idle in my engine is supposed to be about 25 millibar...

Some further good explanation and description in here. They say 100mb for the EA888 but i have some repair documents with photos documenting 25mb. In any case it is a lot lot less negative, than manifold engine vacuum.

 

http://karmakanix.com/knowledgebase/engines/gas-engines-vw-audi/2-0t-engine-tfsi-fsi-audi-vw/2-0t-oil-consumption-pcv-breather-valve/