S6 timing

[UrS4boy]

I guess it could be a split in the rubber hose between the pump and the hatch.

Or a bad mechanical connection between the pump discharge and the internal hose fittings between the pump and the tank access plate.

Like at the Item 3 clamp at the pump or where Item 2 connects to the metal fitting on the bottom side of the plate, as shown in the photo

[HMS-S6]

That's what I was thinking along the lines of.

[HMS-S6]

Yes Dave that would fit the bill. Seems so bloody weird how I got 4 days of it running perfectly last week! It then lost power with AFR showing slightly RICHER. Unplugging the ecu then plugging it back in again showed the same power loss but a LEAN AFR, and that's how it's stayed. Very odd indeed.

[HMS-S6]

Right. Bit of an update; all on the STOCK ecu.

Had a proper run today while someone else was driving to I could eyeball the gauges properly without crashing into snow Tee'd the mechanical gauge into the pipe going onto the ecu.

The fuel pressure is correct! If compared to the mechanical gauge it's spot on
I noticed two things though;

1. If the car is allowed to sit (went to the co-op for bread!) I got ONE GOOD PULL in 2nd with correct power and was a 12.6:1 AFR

2. The boost readout on the dash is reading high by 0.1-0.2 bar sometimes 0.3
PARTICULARLY if in a high gear OR creating load say by trailing the brake slightly. Seems like the further out the reading, the less power I have. This happens on ALL 3 ecu's I have tried. May this be a cause or red herring?

3. You can feel the car pick up every time, every gear at 5,000 RPM at which point the AFR riches up nicely

The problem seems worse in higher gears but this may simply be because I'm in the 'trouble spot' for a longer period.

[UrS4boy]

G42 Intake Air Temp sensor info

This now seems to be intake air temp sensor related, i.e. it runs good when the intake air temps are lower. What is the situation there? What is the deal with your intercooler? Have you checked it for blockages,e.g. leaves, etc. on the forward side of the intercooler?

G42 IAT info: http://forums.quattroworld.com/s4s6/msgs/20996.phtml

[HMS-S6]

Hi Dave,

The intercooler is the 3rd one the car has worn since investigating this problem, this one being checked over after coming form a genuine 55k mile car.

The intake temp has never strayed above acceptable figures and doesn't pull properly even from cold. Today here the ambient is 0 to -1 degrees too. Still doesn't quite explain how I had the car b****y perfect for nearly a week

I've even plugged in a second AIT sensor in the airflow to pick up a false cool reading with no change in the fault characteristics.

I really wish you could drive the car!

[HMS-S6]

I found the out of sync dash display a concern especially since the further out it is (0,3) the slower the car feels!
But since it's tee'd at the same place I can't see how it can be wrong as all 3 ecu's have done the same!
Does retarded ignition cause lean AFR readings? Dmitri has said that a misfire does this so wondered if retarded ignition did the same?
I'm not suggesting the engine is pinking, more that maybe the sensors are detecting another noise on or in the engine? Although they add more fuel, this reads to be a second response, the first is to retard the ignition. After all, my flywheel is now audible in the car at idle and switching off the car.

[HMS-S6]

One reason I ask this is because yesterday while upping the pressure on the adjustable FPR (too high I now realise!) to falsely force the AFR to be correct in my problem spot the car still wasn't anywhere near as 'right' than on its good days I had last week.

[UrS4boy]

Dual and Single Mass Flywheel info

After all, my flywheel is now audible in the car at idle and switching off the car.

"After all"??? First time I have heard this.

The knock sensors are piezoelectric and pick-up vibrations, e.g. those generated by detonation (pinking or pinging). As such, there is a possibility that a worn/damaged dual mass flywheel could generate "noise" that is picked up by the knock sensors *sometimes*, making the ECU think that there is detonation, resulting in the ECU dialing timing back.

Background reading:

G61 and G66 Knock Sensor info: http://forums.quattroworld.com/s4s6/msgs/21047.phtml

Flywheel Chatter: http://forums.quattroworld.com/s4s6/msgs/296566.phtml

Dual Mass Flywheel info: http://forums.quattroworld.com/s4s6/msgs/24536.phtml

7A/3B Flywheel info: http://forums.quattroworld.com/s4s6/msgs/24588.phtml

[HMS-S6]

It's pencilled in for a new flywheel, clutch, slave and gearbox next Saturday.
Dave, do you know if pulling the timing could cause lean AFR readings?

My car was an Audi demonstrator. This coupled with the fact my flywheel is noisey (too much other noise to tell any noise once running) and first gear sounds louder than straight cut tells me that my beloved S6 was probably subject to a hard first year or two 'demonstration' how quick it could take off, probably with sidestepped starts!

[UrS6 - IamS6]

Still don't know much, but I felt, as you are going to do, that to have a clean sheet to test from, the flywheel, clutch and gearbox should be swooped out, as they obviously need to be anyway, the "rattling" is possibly causing the timing to be pulled back.

But having thought that I can't explain why the car was cured for a week, before reverting to "form".

Is there any chance any cables of any part of the loom are damaged somewhere from chaffing or some sort of interference of the cables, which is 'normally permanent, but abnormally not for the cured week'.

Don't pay too much attention to this post, but just wanted to mention the points anyway, as all things, however daft, need to be considered and bottomed out at this stage, given all of what's been checked so far.

Did you get to check the flow of each of the petrol pipes from the tank to the front of the car for flow / no restrictions ?

[HMS-S6]

With the fuel pressure being correct and most parts changed, once the transmission components are all changed, if it still runs poorly I think it'll have to wait for Dmitri to interrogate the car further as there's only so many ways I can try to diagnose it without his know how OR equipment. Especially on such an illusive fault.

[HMS-S6]

And yes, I've carried out the flow test by bridging out the pump so to speak and it was well above the required which is no real surprise since nearly the whole system is now new!
If the return was restricted it would result in higher pressure than desired which isn't the case.

I have the nagging thought of Dmitri spotting that the Load reading was low for my car which would explain it but it's beyond me as to why as the inlet tract is perfectly clear, I've tried 3 exhausts (plus a run without one!), the timing has been checked a thousand times and all is spot on WITH new pulleys torqued correctly.

[HMS-S6]

One thing I noticed today, I know a member on here has spotted it before but I must admit to have dismissed it a little all the way into nottingham I had the missus with the lap-top on her knee reading me stuff, she's so lucky to have me!
The Load in group 000 was 150 max, mostly being low 140's. AIT never strayed above low 20's even after WOT runs! BUT BUT BUT the voltage never reached 14v - the most I saw was 13.3. Is this enough to cause a running issue or is it too slight and another red herring?
Thoughts please,,,,,,,,

[twoqu]

In theory the ecu should have voltage correction built into various functions.
But as previously said, it helps to have the correct voltage (nearer 14V+).
As a quick test just measure the voltage out of the alternator on the big red cable. If thats not over 14V then you have an issue I would say. In an ideal world it would be at whatever the regulator is set at 14.4V usually.