Finally stumbled on a possible for my Volvo 740's backfiring/no acceleration/stalling thing - the exhaust gas recirculation valve. Before that I tried everything - checked injector pulses on scope etc. Even wired in an 'extra fuel' dashboard switch in series with a microswitch on the throttle so it activates the cold start injector just above idle - this does work if the worst comes to the worst and there is still an idle duty pulse on the injectors - who needs an ECU to accelerate anyway? But yeah, not recommended for greenhouse minimisation or fuel efficiency. Anyway the Cat's totally shot so snipping the wires helped - disconnected battery momentarily to reset ECU - what it can't see don't hurt it. Platinum black is a much worse poison than carbon monoxide anyway, and they don't even test for it. Anyway when I blocked the EGR hose & intake nipple connection there was a definite improvement as mentioned in this thread. I'll get around to dismantling the EGR sometime to check out its guts - I don't actually know how it works and why it can affect the fuel mix. I mean the car's obviously got the wrong mix and I've changed MAF's without changing that. So - EGR city.
So what's with the 'former moderator' bit? I mean I hope we aren't going to lose the best mechanic on the web, are we?