Erratic idle and slight missfire when cold.

[Steve940Estate]

Hello
I'm stumped my 1995 940 turbo is misbehaving and I really don't know what's causing it. I have just finished swapping the engine and gearbox plus any associated bits to make my car a manual turbo (it was non turbo auto before).

From cold (overnight) the car apears to run ok. I do about 30 miles at motorway speed, then a short distance at varying speed then leave the car for 7 hours. When I restart the car it idles higher than normal and when driving seems to misfire slightly. This seems to clear as it warms up. I do the 30 miles on the motorway and when I get off the idle is high and only seems to go back down when I sit stationary for a while (normally on the driveway).

I have gone through all the things I can find suggested on here.
I have taken off the throttle body and cleaned it thoroughly and re-set the throttle position switch, that didn't work so I swapped it. This hasn't helped either. I have cleaned the idle control valve and swapped that for another one but things are the same.

I am pretty sure there aren't any vacuum leaks as the pipes are new, I have recently replaced the manifold gasket and injector seals.

Not sure what to do next. Because the problem seems to be temperature related in some ways I wonder if it might be a temperature sensor, although I have read about speed sensor (speedometer) problems as well.

I would be grateful for any suggestions, perhaps the symptoms sound familar.

As I'm in the UK I will have to go to bed in a while, it's 11:30 pm and I've got to be up at 5:30am, but I will be back on here again tomorrow.

Thanks in advance if anyone can help.

Steve.

 

[Steve940Estate]

I swapped the throttle switch last night and adjusted the stops and there is an improvement. Not really sure why at the moment unless the old switch was dirty inside. There haven't been any fault codes saved either.