Hi Jan, check the soldering in the Idle speed control unit. they are known to develop hairline cracks. Just touch a hot soldering iron to the solder traces to reflow the solder. Have you actually checked for 12v power to the ISCV? sometimes know good ones are not good
depends on where you buy them. If you apply 12v to a known good one (usually center wire and then ground each of the other wires in turn (not together
) then when one is grounded the ISCV will wind open and when the other is grounded it will wind closed. if that works then you probably do have a problem with the ISC unit and need to reflow the solder
good luck
Barri