3.5 hotwire strange stalling

Hi all,

Got a bit of a strange thing happening, after my last problem I completely redid the loom and rebuilt the hotwire system and got it running nicely. But at first it seemed perfect but a couple little wierd things have started happening.
First is a stalling problem, normally when deaccelerating it stalls, no splutter and then dead, just off the throttle, revs just fall linearly until they hit 0, no attempt to catch the idle etc. But this is not all the time, often it just falls and then sits perfectly at the target idle. The next is sometimes I come off the throttle and it just sits af arround 1800 and the revs don't drop at all, continue to drive it for a second or two and then clutch in again and then it falls back to normal or stalls as above, all very random. Will do it just at a standstill but normally while driving. The other thing is when coming off the throttle the revs sometimes rise a few hundred rpm before beginning to fall slowly back down to idle (very slow) this all seems a bit strange and random.
Any ideas?
Possibly road speed sensor but why would it be this random?
95% sure ignition is happy.
Dodgy ECU maybe?
Thanks

worth looking at stepper motor and air pipe through to plenum is unblocked and in good condition

jamesmartin said:

worth looking at stepper motor and air pipe through to plenum is unblocked and in good condition

Click to expand...

Thanks, recently have changed it for a fresh pipe so not that unfortunately

and the stepper

jamesmartin said:

and the stepper

Click to expand...

Again, recently cleaned and tested but I'll have another look.

I would suggest take a look at throttle potentiometer - check base voltage then look at resistance and scaling. The other thing I would check is the vac advance and vac advance hose. Do a suck test.