Since winter arrived here Tuesday, my '90 740 wagon, non-T, stumbles and dies several times when started cold, then after 10 or 15 seconds establishes the right mixture and runs fine. The car occasionally had this condition in a milder form before the mercury plummeted, and I just finished cleaning the throttle body Sunday, when it started and ran well immediately in the garage. Can't find any loose vacuum hoses, so I suspect the IAC. The car has a Rex Regina system, with a VDO IAC, Volvo pt. # 1389 557 printed on the label. It appears to be sealed, so I don't know if squirting carb cleaner in there and swirling it around as described in the FAQ might make things worse. Hate to pop $200 for another, unless I get lucky and find the right Regina in one of the local boneyards. Does anyone know if this part is used on other cars, or if there's a reasonable substitute? And is it safe to try cleaning it? Thanks.

I cleaned the one on my '92 745 with carb cleaner and it improved idle.

I Had to do it several times because a lot of grime came out.

Also clean and tighten electrical connector to the ECT sensor.

It this fails check the ECT itself.

Not sure that the idle air system would control the mixture. I rather think it maintains the idle speed under varying conditions at 750 rpm and 900 with AC on. Not sure but it may raise the idle speed right after starting but you can do the same thing with your foot on the throttle.

Have you thought about the engine coolant temp sensor which does enrich the mixture to a cold engine after starting.