S6 timing

[HMS-S6]

Yes and he is taking some logs for me tomorrow. So although they will be slightly different it should at least tell me if mine are somewhere near right.
If this checks out ok, I'm heading towards unmetered air being drawn in (although I'd struggle to see where since I pressure checked that hose to 1 bar AND drive the car with all the junctions to it plugged!)
OR
even with adequate pressure the injectors aren't being provided with what they need?

[twoqu]

I am struggling to see how/where unmetered air could be drawn in without it leaking out under boost! Even something like the injector seats. Would have to be after the maf and not shown up by pressure testing.
I was going to suggest the turbo housing O ring on the compressor but cannot see how it would fit the symptoms!
Although it might have something to do with the high vac/full boost technique which you say allows the car to function correctly when you come off/on the throttle.

[HMS-S6]

I know!! Annoying as its defying logic at the minute. I upped the fuel pressure the other night and it richened it up AND improved running which kinda proves the symptoms but obviously I shouldn't need to do this for standard SW! Very odd.

[twoqu]

Of course what we are calling excess air might be the boost! Its almost like the ecu is not seing the boost and therefore not making any adjustment. Then again I am not sure the map sensor has anything to do with fueling as thats the reason for the two boards! The demand for the air is measured by the maf. The more it sucks in the more fuel it adds, oversimplifying it somewhat!
The low 14 afr is almost like a cruise figure. Be useful to calculate what the ratio between what you should have and what you are getting represents in terms of fuel requirement. Sounds like a considerable amount.

[HMS-S6]

We are on exactly the same thought!! I agree 100% that the car isn't fueling to match its boost but until I know what duty cycle ROUGHLY other stock cars are showing in my trouble spot I don't know if it's not TRYING to richening up or its trying and CAN'T. See what I mean or an I just lost in my own mind? Lol

[twoqu]

Yep! The boost signal for the in dash gauge comes out of the ecu so it must be seing it!
Seems reasonable to compare similiar cars. As you say if the ecu is requesting the right amount of fuel but not getting it, what else could it be other than the injectors now. Other than voltage which the ecu can make adjustments for and earth, the only other thing is perhaps blocked filter baskets or an actual detioration in the windings.
Sorry I can only offer stupid ideas and some support!

[HMS-S6]

My friend (ex-boss) has an asnu and is back in 3 weeks so can check injectors then (even though they've been substituted off my good car once). But yes, despite good flow and pressure it can't hurt to remove the pump basket to look for anything obvious.
Also tomorrow I will triple check the throttle switch but last time I had vag-com attached, it was showing 99% at WOT.
And no, thanks, it's nice to have a second brain to bounce ideas off!

[twoqu]

The only other thing that was bothering me was the air escaping from the oil filler cap when pressure testing but not entirely sure why!

[HMS-S6]

It was entering the cam cover via the breather when testing the MAF hose. I was doing it wrong!

[UrS4boy]

AAN boost leak testing options

It was entering the cam cover via the breather when testing the MAF hose. I was doing it wrong!

Previously posted:

http://www.s2forum.com/forum/showthread.php?t=63987&highlight=AAN+boost+leak

[HMS-S6]

Thank you.

[HMS-S6]

Just running an idea! Even with pressure AND flow, is it possible to still have a fuel delivery problem?

[UrS4boy]

Just running an idea! Even with pressure AND flow, is it possible to still have a fuel delivery problem?

Certainly. It could be a pump or a pump inlet clogging issue *OR* it could be a kinked fuel line. Who knows.

What you could do is at least check the fuel pump for debris (rust) around the inlet. Maybe in motion, the tank has debris that gets stirred up and sucked onto the inlet screen, limiting flow into and out of the pump. Something that doesn't show up during a static fuel pump test.

You could use this 19 page pdf that I wrote regarding C4 fuel pump testing and replacement as a guide:

http://12v.org/urs/Fuel%20Pump%20Testing%20and%20Replacement%20ProceduresRev3.pdf

[HMS-S6]

I have driven the car with the gauge resting on the screen so I can read it but I'm still going to take a look inside there. I have had it on another car where it was drawing air so although it had pressure I was a fuel/air mix, but this car WASN'T a submerged pump so I can't see this is possible on an S6??

[UrS4boy]

so I can't see this is possible on an S6??

Cavitation is one possibility if the inlet gets clogged. The sucking of the pump across the clogged screen could lower the pressure on the back side of the screen to the point that vapour pressure is reached and bubbles form.

"Cavitation is the formation of vapour cavities in a liquid – i.e. small liquid-cavitation-free zones ("bubbles" or "voids") – that are the consequence of cavitational forces acting upon the cavitational liquid"