Folks,
Since the weather has turned cold I've been experiencing Code 25 (Air-fuel lean malfunction) and the car being very reluctant to move off when cold. This doesn't happen every day, more like every second or third day, so it isn't one of those that is just an annoyance.
 
If I drive for around a kilometre and turn the car off then restart, the engine light goes away and the car runs normally. I always wait until at least the cold start injector has gone off (idle speed picks up slightly after about 20 seconds) and sometimes wait until I see the temperature needle has started to move, so the car isn't dead cold when I roll out of the driveway.
 
I've worked my way through all the wiring and vacuum lines, and have even opened up the ECU to look for dodgy capacitors, but have found nothing. I'm starting to wonder if the AFM (flap type) is sending lower than actual readings. I also don't know how the system could be determining that the system is running lean, because I don't think that the O2 sensor (single wire) would have warmed up enough to be sending useful signals so soon after start-up. The O2 sensor is only 6 months old, so is unlikely to be faulty.
 
Has anyone else experienced this, or have any ideas on what could be the cause? Any help will be much appreciated.