You can't have your cake and eat it!

[bernsaudi]

Hello, since putting in my aan engine and chips from hoffer, I have had a dilemma.
If I leave the lambda attached (which is new and I can see it cycling ok but has a few lean patches in the throttle spread) I get really good mpg(over 28 to the gallon) but it doesn't run right under power, and sits at idle burbling and missing occasionaly. I drove it like this to Nurburg, and by the time I got to Belgium(well hammered a few times) fuel starvation and really bad idle was the norm with adaptation limit not reached codes.
Cleared codes, better till another thrashing.Also pinking resident ...

Took it round the ring for a lap like this and it was awful....Anyway after having beers etc I decided to disconnect the lambda to indulge my annoyance and the car was transformed into a raging monster(I like it)...However under normal driving the mpg is about halved..and thrashed is down to 4 ish to the gallon(ring figures so I dont mind).

My motor has a 'stage 2 rs2 turbo' from the aet paperwork, fitted at the same time as the engine/ecu change. When it was chipped and standard it did almost as bad on fuel as the lambda off situation so I am pleased with the new facility to run on great mpg but now I want to at least make it happy with the probe fitted.

I am going to catch up with hoffer soon when I get the chance, but I'm just wondering if this rings any bells with anyone?

It really does go well with the probe off though, and the pinking is not audible.

What I dont get is that it doesn't miss at all with the probe off(coils are ok then). I havent changed the fpr yet(3.8)..I would think that but again, it doesn't miss at all and is strong with the probe off..
Ta ra!

[Jamo]

That doesn't sound right as under WOT the car should be running open loop ( i.e not using lambda ) and not closed loop which it will under part throttle.

If the car is peforming differently under WOT with the lambda disabled are you sure the ECU is seeing WOT?

[bernsaudi]

This is when it would be an idea for me to have a proper vagcom rather than just a vag reader. Forgive my ignorance but is the wot something that can be checked visually and with a meter? If so I'll get at it.The thing is..its the way it is generally burbly and weak throughout the normal non WOT throttle that is (i think) aside from the WOT stage. you dont have to give it the beans at all to feel it is lean.

[Rusty]

Jamo speaks the truth @ WOT it runs open loop as it's a narrowband O2 sensor. It's more than likely that by disconnecting the ECU that the ECU goes into a basic setting and this is why it's running better, it should run rich (safe) and this will mask your issues. Pinking would indicate incorrect timing or lean running, both are possibly hazardous so if it were me I'd be getting this sorted pronto before holeing a piston or worse!

Step 1 is to check for fault codes.

Step 2 is to clean up the MAF in case it's filthy, I had to do this on my car after re-fitting the MAF, it was covered in goo and the car wouldn't run with it attached, cleaned it up and all good now - I blame the volcanic ash cloud for that one I think it couldn't get the mixture to adapt enough to the erroneous signal. After this reset the ECU by pulling the motor fuses for a few mins.

Step 3 is to get the AFR measured with a wideband lambda probe that is know to be calibrated and accurate, this will highlight any running issues that your more empirical methods seem to indicate the existence of.

Step 4 is to get it tested on a rolling road and see that all is well.

[bernsaudi]

Hello, I've got two cleanish MAF's and the result is the same, also the output looks nice and clean on both.At the moment if I disable the wgfv and plug the probe in it becomes docile(6 psi on the gauge) and no pinking, so until I reach civilisation it's safe for normal driving.Running rich with the probe off otherwise is also good for the short term, cuz it dont pink at all, problem I have is work and distance from solutions....
AFR...dont yet know a great deal about that yet but willdo soon..

[quattro]

You will regret running the car like this, if its running like you say it is stop driving it.

[Keeper of The Kitten]

Just one other suggestion to throw in the pot here - is the throttle actually opening fully? I had my throttle partially stopped by an incorrectly fitted jubilee clip way back in the past, it is worth checking.

[HPmuirt]

What is the most likely cause of 'adaptation limit not reached' errors?

Cheers n

Si

[Jamo]

Just one other suggestion to throw in the pot here - is the throttle actually opening fully? I had my throttle partially stopped by an incorrectly fitted jubilee clip way back in the past, it is worth checking.

That what I said WOT= Wide Open Throttle.

You need to have Vag-Com and check to see if the WOT code happens when you pully press the pedal

http://www.s2central.net/vagcom_4.html#Read%20Measuring%20Blocks

Block 04 Throttle Switches

Fault = 00000

Idle = 00010

Part throttle = 00100

Wide throttle = 10100

Overrun = 00011

[Jamo]

What is the most likely cause of 'adaptation limit not reached' errors?

Cheers n

Si

Dodgy lambda sensor or the car is running injectors not meant for the ecu map so during closed loop the ecu can't reduce or increase the fueling amount enough to hit the target setting.

Try reseting the adapting as per s2central.net

Reset Adaptation

A number of dynamic 'adaptation tables' are maintained by the Motronic ECU. These are used to make minor adjustments to the engine's ignition, injection and boost parameters to account for things like variations in fuel quality. Over time the ECU builds up these tables with key parametric information as the car is driven in order to try and optimise performance and fuel economy for the prevailing conditions. This intelligence is partly enabled by the 'closed loop' system of operation that the S2 engine has with the use of its heated lambda sensor that determines the fuel:air ratio. The Motronic ECU monitors this ratio and adjusts the ignition and injection timing accordingly. Wonderful things them silicon chips

This is primarily how the S2 ECU can run happily on either 95 or 98 RON unleaded fuel, as it dynamically computes the optimal ignition & injection settings based on signals from the lambda and knock sensors. If desired, these dynamic adaptation tables can be reset, with VAG-COM, in order to force the ECU back into a default condition whereby it will commence the dynamic learning process all over again.

This system is vastly superior to the scheme of using 95/98 code plugs that some other car manufacturers use on their engine management systems for two reasons -

1. No driver intervention is required to tell the ECU that it is running on 95 or 98 fuel

2. A binary code plug system cannot effectively handle situations with a mixture of 95 & 98 fuel in the tank

[Keeper of The Kitten]

Haha! Fair point - I was thinking physical WOT and not thinking about if the throttle pot saw it the same as the physical ...is there an adjustment for the pot that could also affect this?

[s2_bo]

I wouldn't drive the car like this, worse case scenario would be melted pistons the Lambda is needed even more so if its chipped.

[bernsaudi]

Now i've put it to mechanical boost it doesn't pink(can't I suppose with only 5psi boost) and put the probe on, slowish but happy till fix time!! Might even do well on juice till I can find some 98 ron(don't do it round here for 60 miles!)....

[bernsaudi]

Sussed it!! The simple thing!!

Hose from manifold to ecu had aged, found it when the idle pipe blew off!! The car is wild now.....Smiling...

I have done 5000 miles with this conversion, it does 25-30 mpg, and the car is wild and thirsty when requested...Credit where its due Hoff, this goes like stink now!! Thanks

It just goes to show that sometimes these problems need to be considered more subjectively, and that is tough when you have been thinking too hard about your pride and joy!!

Think I need a rear anti roll bar now.......

[macspring]

Thanks for remembering to post the cure for the rest of us.

Enjoy.