Hi, did a bit of wiring checking - and got my oil temp MFA back - which was wired to the coil lol I do have a random green wire not attached to anything coming through the firewall under the coolant expansion tank. The coil is all wired up according the the Haynes now (although my experiences with that book have been, well, mixed!) Despite the idle switch passing the resistance test - I think either it or whatever it controls is the problem. Tried starting her up with it unplugged and the problem of rough running/stalling under light throttle went away (obviously revs were dropping when closing the throttle when cold as I assume whatever the switch is supposed to do would stop that) The switch has appropriate resistance to the right terminals when throttle is open and closed so it's probably not the switch itself. I tried an alternative ignition module - no difference. What next? I do have an ECU of unknown working ability (somewhere!) - I'll dig that out and try switching it over.
Changed the ECU around - no change - so I guess I will try getting hold of a switch and see if it was that after all
I think part number is 027 133 061A - looks like £61.98 from VW classic parts Can't find any aftermarket eBay specials unfortunately. Unless anyone knows different I guess I will just have the bite the bullet and hope!
hmm. have a look at the ignition switch wiring next, make sure its correct. helpfully the plug picture showing pin numbers in the hanes manual is incorrect, sop check the plug itself it will have the pins numbewred for you. 1 - white - to cold throttle enrichment 2 - black - ignition live 3 - black/yellow - to ECU and ISV controller then test the switch electrically, if it comes out ok then you shouldnt need to replace it. 2 and 3 should show continuity throttle closed, 1 & 2 no connection. then 1 and 2 continuity throttle open, 2 & 3 no connection. to rule out any issue with cold throttle system unplug the valve behind the airbox, its the metal one with black and white wires to it. while back here check the wirign over carefully for damage
Awesome - solved! Thanks!!! You just saved me £70 and more searching! Assumed you meant idle switch Continuity on the idle switch as described. My black and white wires went to the deceleration cut off valve (027133985A) and the metal thing had black/yellow and brown/black . Assume that's the wrong way around?! Swapped them over and problem (seemingly) solved! I'll run it up to temperature properly over the weekend to make sure. Is that solved or have I proved one or the other valve is faulty?
yep thats the wrong way round! I was sure I mentioned which wire colours go where to these in my guide, but it appears not. I'll add that info in now
I had a look back - I noticed the wire colours in the guide now I guess I just overlooked it or misidentified the valves they are plugged into! Thanks for the help!