BennyT

For the record, I think I've identified the problem - indeed an ECU problem. It looks like the ECU was still in A/F closed loop mode when I had some ignition problems (likely due to bad coil pack(s) and / or bad loom and earthing). As a result the fuel correction map seems to have over compensated and thrown the fueling out (probably got screwed up by the misfiring, maybe even bad AFR readings). Having deleted the correction map, AFRs have returned to "normal" (actually they're now too lean but I will remap in due course). No garage trip required just yet

Sure thanks. I'm sure it's gonna be plenty of money either way

Hi folks, I'm getting kinda demoralized here. TL;DR Car is running too rich after some rough running that seems to have gone away. No idea what the cause is. Car is modded R33 GTSt, FCON Pro, MAP sensor, stock (untouched) block (see also my other post ). Few weeks ago did a long journey, mostly motorway cruising, but some small bumpy roads at the end. (It's possible something got wet or shaken loose...). Car was fine. Next morning fired up and immediately running rough, kinda chugging at idle (never done this before). It steadily improved with some light throttle. I couldn't see any problems - but I was away from home and needed to drive. I bimbled up the road and it had some hesitation but settled down. Driving started with occasional hesitation but pretty much cleared up (but not entirely). All of this at low revs but there wasn't a problem with increasing revs. I made the long journey home again with almost no issues (hesitation only a couple of times at steady / low revs). The only other obvious symptom was that it is running rich, like ~6%. For steady cruising, the AFRs on my wideband are about 13.8-14.1 and should be about 14.8. Without finding anything obvious I suspected ignition / coil problem (being over 20 years old!). All spark plugs looked fine (maybe a bit black but they're not old, HKS brand.). So I did the R8 coil conversion (plus new ignition harness) but no change in rich mixture. However, any hesitation seems to have stopped. In fact, the car seems fine except for still running ~6% rich. Why is it rich?! I have checked a few things: Fuel pressure is good (from cockpit pressure gauge). The engine temperature sensor seems fine (resistance and voltages check out), I have cleaned and replaced the engine earthing and I cannot find any loose connections or air leaks. I also replaced all the top breather pipes. I have tested the coldstart valve by blocking it and it seems to behave correctly (i.e. no effect once warmed up). Now, not sure best plan of attack. There could be an air leak (guess I need a full leak down test for this?) or electrical problems with the MAP sensor or ECU but I don't know how to easily test this - plus it's running fine. (I will remove the FCON entirely and go back to sock ECU for a road test, not done yet, although maybe not very helpful since mapping will be different). What else can I test without buying spare parts or a costly and complicated trip to the garage? Thanks

SOLVED! (At least partially) Thanks, yeh I have spec 2 so no igniter module. So with further digging it turns out the R8 coils need a lot of juice. I asked a knowledgable chap about the FCON and he pointed out there were some options to mess with the ignition signal. In fact, jumper 11 (J11) inside the unit switches between "normal" and "high" current mode. (I can only speculate that "normal" mode provides some safety in event of a current surge.) Evidently the stock ECU provides enough juice as standard. Anyway, I switched to "high" current mode and it worked just fine. I still don't know if my original ignition problems have been solved by the new coil packs but this seems like a step in the right direction. For future reference, I noticed that the stock ECU throws ignition fault code 21 when using the FCON (I think this maybe normal operation due to the by-pass?).

Nice find! Huh, weird. I guess it's possible. FCON Pro is supposed to be a pretty comprehensive ECU (in it's day!). I wonder if anyone can confirm this... ? It was weird there was no spark at all.

Hi folks, Spec: R33 GTSt Spec 2, FCON Pro (piggy back) with MAP sensor, top mount turbo and supporting mods otherwise stock (unopened) engine. I do my own tuning on the FCON and have been running it for a few years. (The mapping is good). To cut a long story short, I developed some fairly random igition problems at start up / idle and basic driving (no boost). The stock ECU was thowing fault code 21 (ignition) after just firing it up (no driving). I figured I'd do Audi R8 coil swap, since the coils are original anyway (25 years old!). So, with the R8 coils fitted, I fired up. Zero ignition. Engine just turned over, no spark at all. So I removed the FCON entirely to check the stock ECU (switched back to stock AFM) and ... ... fired up perfectly. No error codes thrown. So, why does the FCON fire the stock coils but doesn't fire the R8 coils? Ignition dwell time is about the same for the stock and R8 coils so shouldn't be a problem. I can only assume the FCON or the wiring harness has some kind of weird problem... It's possible that the FCON got corrupted somehow but it looks OK on the laptop and it's not throwing any error codes. I'll probably have to check the harness more carefully although I can't figure out how it could have got damaged. Maybe I should just bin the whole lot and get a Link? It's just a shame they're so expensive... Thoughts? Thanks