Well, yesterday I spent the day at Brands Hatch on a track day round their Indy Circuit which for the most part was a good day, though not without its issues
After a few sessions out on the circuit I noticed my AFR suddenly jump up to 18-19.5, regardless of whether I was sat idle, cruising or on boost. I brought it straight back in to let it cool down for a bit and contacted Bill for a few suggestions.
A scan with VAG COM didn't reveal anything, though earlier that morning when clearing an EML for EVAP I did notice this little beauty as well:
16518- Oxygen (Lambda) Sensor B1 S1: No Activity
As my AFR seemed fine I hadn't really thought much of it but looks like it could be a broken pre-cat sensor or damaged wiring. I'd wondered if the wiring had even got too hot from the downpipe, though the readings from my wideband were so erratic it didn't match any logical pattern, just did what it pleased. Measuring block 001 on idle showed lambda to fluctuate between -3 and 3 while AFR was showing 16-17 which didn't seem to be abnormal so then I began to question whether my wideband sensor was lying to me, though the fact I logged a code for the lambda would make me more suspicious of this. The car continued to run fine throughout the day, no spluttering etc. A good check under the bonnet also revealed that no hoses were split etc and the characteristics of the very sporadic readings swayed me more towards an intermittent electronic issue.
I rang the nearest ECP to see about getting a new pre-cat lambda sensor to give this a go but they only had one Bosch one left in stock across the country and that was in Wembley, meaning if I were to go and get it by the time I got back to Brands the day would have been over. In the end I just waited for the AFR to sort itself out and got in what little track time I could.
With a passenger keeping a close eye on the gauge while I went round we found that the readings could go from perfectly normal (~11-12 on full boost) and then jump straight up to 18-19. If we limped back to the pits and sat there it would sometimes then sort itself out, very very erratic
For now I've ordered a new sensor so I can perhaps fit it sometime over the weekend and see whether this helps anything. A quick scan when I got home last night showed a repeat of the above code so assuming the wiring is all OK when I get underneath to have a proper look then I'll start with this and go from there.
Aside from this the car was running really well, managing to out run two B7 Audi RS4s on the straights which I was really happy with and the car felt nice and planted through the corners. I'd really recommend the VT rear beam bushes to anyone still running OE as the back end just seemed to stay exactly where I wanted it all day. I'm not 100% happy with the brakes at the moment, which felt like they were fading after a few quick laps but it's actually just the pedal feel that goes a bit spongy while they still stop just as well. I was hoping for firmer feedback really as it didn't inspire much confidence until I was used to it but all in all I'm very pleased with it.
Unfortunately the official photographer didn't make an appearance this year which I was really counting on, but a friend managed to get a small amount of drive-by footage and I also tried using another mate's in-car camera for the last session which I'll try and retrieve the video from when I get the chance.