Correct AFR

[S2central.net]

Also worth trying a 2nd MAF to see if you get same behaviour !

[prj]

Dmitri, Just refitted the stock ecu to my car and went for a run with the AFR rigged up. As it comes 'on' at around 3000 rpm (1bar) the AFR goes to 13-13.2 as it is hessitating, as it clears at around 4,500-5000 rpm at goes to high 11's-low 12's. Would you say that its lean running causing my issues?

Sounds like you have a misfire there where it is hesitating. Misfire always shows as lean on the AFR gauge.
Also stock software does not run 11's anywhere, it should be 12 or up.

Btw, if it's fine from cold and then gets bad when hot, then it sounds very much like the coils at fault. When the coils start going, they start first misfiring when hot under peak torque.

What coils did you have again? Maybe time to order a plug and play coil loom from efiexpress.com?

[HMS-S6]

Ive had a fuel pressure gauge on there before and its reads exactly what id been advised it should on here (3bar plus boost??). Maf, i have tried three but now the boost leks are cured i may try another again.

[prj]

I do not believe you have any issues with fuel pressure or MAF.

[S2central.net]

On the S6 - the correct fuel pressure is 4bar +/- boost/vacuum... so you would see 3.5bar at 0.5bar vacuum and 5bar at 1bar boost.

BUT - have you actually checked the fuel FLOW rate from the pump - its easy on the S6 as access to the lines is more user friendly.

prj has a valid point too on the coils... easy to check/replace with a 2nd car alongside before gambling on new set of COPs etc

[HMS-S6]

Dmitri, No, its pretty **** when cold too mate, just gets WORSE when its warm! I have tried a second set of coils from a car that ran perfectly and it made no difference though.

Is there and way i can determine whether its a fueling or ignation problem?

[HMS-S6]

I do not believe you have any issues with fuel pressure or MAF.

Dmitri, Would you take a punt at coil conversion kit if you were me?

[HMS-S6]

On the S6 - the correct fuel pressure is 4bar +/- boost/vacuum... so you would see 3.5bar at 0.5bar vacuum and 5bar at 1bar boost.

BUT - have you actually checked the fuel FLOW rate from the pump - its easy on the S6 as access to the lines is more user friendly.

prj has a valid point too on the coils... easy to check/replace with a 2nd car alongside before gambling on new set of COPs etc

I'll double check that pressure.

How do i check the flow and what is the correct value?

[S2central.net]

As per this - http://forums.quattroworld.com/s4s6/msgs/22623.phtml

You are looking for more than 650cc delivered with the pump held on for 15seconds and 12V at the pump... best done with a relay jumper in the fusebox - look at the graph in the link above.

[HMS-S6]

I do not believe you have any issues with fuel pressure or MAF.

Can i get the Coil kit in the UK?

[S2central.net]

If coils from another (known good) car made no difference then rout cause of any misfire must be in the POS / BIM or the ECU itself - unless you have a wiring / earth issue between ECU and POS/BIMs... Have you tried swapping BIMs or ECU with a healthy car ?

I only suggest those methods as most cost and time effective way of component replacement that could help root cause this one.

As long as you do things in a logical sequence and take good notes of any different behaviour you should be golden.

There are only six things at play here...

0. mechanical timing (correct phasing of camshafts to pistons via timing marks and toothed belt)
1. air measurement
2. fuel delivery
3. spark generation
4. ECU software (which encompasses all the various sensor inputs and timing of course)
5. The wiring which links it all together

I would stick with OE software while you are fault finding to rule out one massive variable (especially as source of chips is unclear)

[prj]

Dmitri, Would you take a punt at coil conversion kit if you were me?

I would most likely know exactly what it is after doing 1 WOT run, but I don't have the car here.
I don't want you to buy coils just because I said so on the forum based on some info that could go either way. If it doesn't help then you're 400$ or so poorer for no reason, I'm not taking that responsibility. You're talking to a B5 RS4 owner though, 400$ is a tiny drop in the pond

Most likely nothing wrong with your POS/ECU wiring, because that would be there all the time, not only on WOT.
As for checking other coils on your car - you had a boost leak before, now it's fixed, might have been masking the problem.
Also, if your plugs are not the newest, then checking other coils might not do much. All these coils are mostly over 20 years old. There could be very little difference, and they could run fine on another car, and not on yours.

All that said - getting worse when the car gets hotter, hesitating at peak torque, lambda meter showing lean, getting worse when more boost is applied (via chipped ECU) points to coils and a plug and play coil loom is a sound investment if you wish to keep the car for a long period of time regardless.

[HMS-S6]

I was more thinking on the lines that; if I get the cool over kit at least I'd KNOW it wS ok, plus I plan on at LEAST RS2 spect one day so they'd be a good investment anyway!?

[HMS-S6]

Can I get this kit in the UK or will I have to get from the states?

[newsh]

I got a wiring harness from Error404 and the coils from here http://samtechperformance.co.uk/pres...roller=product

There is also an eBay seller whos does a complete kit.