S6 timing

[newsh]

I know you've pressure tested but ... The small vac line which goes to the FPR from the inlet manifold, I think on the AAN there are 2 short pieces of cotton covered vac tube and a chrome plated hard line. If one of those 4 clips is a little loose and the rubber tube has gone a bit hard, then you can pressure test and get no leaks but go vacuum and it moves the pipe a bit and it leaks, next time you go on boost it may leak or it may not. I had this on the vac line to my ECU, the clip was done up tight but it leaked sometimes after lifting off and going back on boost. If the leak is in the line to the FPR then it will go lean on boost and occasionally rich on idle.

I guess you're probably going to reply that the hose and the clips are all new! But it's worth a look just to see.

When you pressure tested, did you finish up with soapy water and look for bubbles?

[HMS-S6]

Yes mate, the garage I previously worked at checked them out then ultimately swapped them for set off my other good S6 and both cars remained exactly the same as before the swap. I'm currently trying to find out if it IS actually lean or the spark is poor. My understanding is that the AFR shows the same for both conditions?

[AndyP]

Have you had the injectors checked? There must be somebody in Nottingham with an Asnu machine that can check them?

[HMS-S6]

I know you've checked the fuel pump with a static flow test, but could it be faltering under full load? Try relaying the pump or fitting a pressure gauge so you can check pressure under load.

Hi Andy, thanks for the input, last year at some point I ran it with a gauge attached and it was spot on. It's also had a new Audi pump at the same time and a new FPR yesterday.

[AndyP]

I know you've checked the fuel pump with a static flow test, but could it be faltering under full load? Try relaying the pump or fitting a pressure gauge so you can check pressure under load.

[HMS-S6]

If the earth is good and I have battery boltage to those pins am I to assume the spark generation isn't the problem? I.e Is that as much as I can check in this area?

Just send down my local bypass, held it at 4,500, went to WOT and it pulled ok up to redline with 13.5:1 AFR (roundabout) was fine in 2nd 3rd 4th and 5th, changed to top and it went flat again and the AFR showed 14.8:1 at 5,500RPM at WOT. Something sure isn't right.

[UrS4boy]

Hi Dave, I've just yesterday ran a lead from those equivalent points to the body and now have perfect continuity. I'm going to re Earth the coil harness next but right to the battery to rule out anything!
I've got a 2.0 TFSI coil conversation on it, at what point do I measure the voltage that the coils are being fed Dave?

Sorry. That ground diagram I just posted was for a 3B (and presumably ABY and ADU), not AAN. The AAN engine harness grounds are at the right rear corner of the cam cover (1 wire) and the intake manifold (2 wires IIRC). The engine to chassis ground is under the exhaust side of the engine, under the turbo, to where the right engine mount is located.

As for power to the coils (OE or pencil types), it is in the white connectors on the firewall connector rack. They should show battery voltage with just the ignition turned to "ON" (run).

[HMS-S6]

Is there a way I can determine if its actually lean running or poor spark causing my lean AFR reading??

[HMS-S6]

Hi Dave, I've just yesterday ran a lead from those equivalent points to the body and now have perfect continuity. I'm going to re Earth the coil harness next but right to the battery to rule out anything!
I've got a 2.0 TFSI coil conversation on it, at what point do I measure the voltage that the coils are being fed Dave?

[UrS4boy]

You could unbolt the ground wires at the Inlet Manifold, I'm assuming they're in a similar place to the 3B and ABY, under the IM near the throttle body end, check for fraying and cracked insulation and give them a good clean, copper grease and bolt back up.

Does this help in some way?

[HMS-S6]

I'm also going to make sure the could are supplied with a full feed.

[HMS-S6]

I will try earthing the engine direct to the battery just tempo just to be 100% sure!

Also, on the coils front, I hear what you're saying about the software but they're only 2 weeks old and are the newer red ones and brand new.

[twoqu]

Isn't max torque max cylinder pressure? Although I am not sure what effect that has unless it is spark related.
If the S6 is like the A6 it has relatively poor engine ground. It's not going to hurt to clean the engine earth cable which runs from the engine mount to a boss on the chassis rail undernath which is prone to corrosion.
If you have relayed the fuel pump from the battery then it effectively has its own ground from the battery direct to the chassis.
Alternatively you could attempt to rig up a jump lead from a good eath point on the engine to the chassis just to test the theory. I was also wondering previously whether the alternator voltage was dropping which would effect the coils and injectors. The injectors have a voltage compensation I believe but in theory less voltage would mean less fuel unless a compensation was applied. Not sure whether its the same for the coils.

Of course unless the coils are known good there is the possibility that they have been damaged by the excess dwell time on stock SW. They only use @50% of what the stock ones do so their life expectancy is less.

[HMS-S6]

14.3 at 3,500-5,000 on WOT then richening up a little above that RPM but not much.
Am I right in thinking that's WAAAAY to lean?

[newsh]

There should be a ground lug on the TFSI coilpack harness, make sure that where this is bolted to is clean. Continuity from this lug to the chassis (and battery neg) should be close to zero Ohms. Power to the individual coils is supplied by the two 3 pin plugs (one with 2 pins one with 3) AFAIK this should be same as battery voltage.

You could unbolt the ground wires at the Inlet Manifold, I'm assuming they're in a similar place to the 3B and ABY, under the IM near the throttle body end, check for fraying and cracked insulation and give them a good clean, copper grease and bolt back up.

I am swaying towards spark issues, years ago my 3B coupe had a similar issue of missing at max torque which turned out to be plug leads.

I forget did you try different plugs?