Came across a new-to-me vacuum leak fault this morning that looks likely to be a common one on the 6-valve 3-cylinder engines as these cars get older. It was on a 9N3 2005 Polo, but same engine code is in plenty of Mk1 Fabias.  The AWY engine code that preceeded this one is probably similarly vulnerable.

 

Owner was asked "are there any fault lights on" and I was told "Oh yes, been on quite a while"

So VCDS Lite was plugged in and revealed 

3 Faults Found:
16555 -  Fuel Trim; Bank 1: System Too Lean
        P0171 - 35-10 -   - - Intermittent
16490 -  Manifold / Barometric Pressure Sensor (G71) / (F96): Implausible Signal
        P0106 - 35-10 -   - - Intermittent
16725 -  Camshaft Position Sensor (G40): Implausible Signal
        P0341 - 35-10 -   - - Intermittent

 

I must admit I was surprised not to see a 'cylinder 2 misfire' code instead of all that, 'cos I've previously replaced coilpacks 1 & 3 on this car.  I also viewed and logged a few parameters to see what was happening, and the inlet manifold pressure was a god chunk higher than I would have expected at idle, somewhere around 360mbar.

 

Anyway, set about looking for air/vac leaks and found one, not one I've seen before. 

The servo vac hose was bodge/temporary repaired with gaffer tape at least a couple of years back, and that repair is still in place, and not leaking.  Not that.

Tested the effect of putting a finger over the pressure equalising port of the PCV valve and no effect, so that was passed.

Happened to knock the output hose of the PCV valve as I moved my hand away from the previous test and heard a pronounced hiss/suck sound, accompanied by the engine bogging down.

Aha!

 

The shiny black plastic hose here is the one I knocked, and subsequent fiddling showed that an upwards knock near the steel pipe end had most effect.

 

And this is why (hose actively held upwards from its resting position):

 

Gaffer-tape temporary repair was enough to prove the point:

 

The car initially wasn't at all happy at low revs, bogging down badly, but a few minutes running with a few on/offs and it all settled down. No fault codes returned during a short test drive.

As a bonus, and not surprising to me following a similar situation on our Fabia last week, the brake servo suddenly got much more effective!

 

Not sure what the best long-term fix is, presumably some rubbery hose of oil-resistant material, of a size that'll fit both metal pipe and hard plastic section.

Item 38 in the diagram here; 03D103606L appears to be the part number of the genuine item, but it's spectacularly overpriced if this is anything to go by: https://www.allcarpartsfast.co.uk/vw-audi-seat-skoda/vw-audi-seat-skoda-03d103606l-venthose/

That's just one of the rubbery joining bits, not the whole assembly! 

I suspect the gaffertape solution will remain there, knowing the owners. And it'll probably be fine.

 

 

 

 

 

 

 

 

 

Nice work. Looks like a bit of coolant hose would do.