I posted this question weeks ago in the 900 section but no one has responded. I hope someone here can help since 740/940 are basically the same.

I have a '93 945 Turbo (B230FT) that has had a cold idle problem for 2 years.

After recently replacing the MAF, the car is consistently running fine and the sometimes erratic idle has improved.

However, now that it is fall and morning temps are in the 30s-50s the idle surge is back.

Here are the symptoms:
Car sits overnight and starts on first crank 100% of the time. Idle is steady. I drive away, stop at a red light 3 blocks from my house and the idle surges between 600-900 RPM for about 10 seconds. It evens out and idles fine for the rest of the day. If it is colder, it surges longer and the idle does not even out unless I'm driving and the engine warms up a bit. I have also found that if I start the car and let it idle for a few minutes before driving away, it will surge. This happens in winter if I start the car and have to scrape ice or brush snow off for a few minutes.

Here's what I've replaced:
- Mass airflow sensor (MAF)
- main fuel pump and fuel filter
- cap, rotor, plugs (NGK copper)
- swapped idle air control valve***
- oxygen sensor
- all vacuum lines
- cleaned flametrap
- cleaned throttle body
- ran seafoam through intake

***I must qualify the idle air control valve swap. I have 3 IACVs. They are all used and I have cleaned them all. The car runs exactly same with any of these 3. I believe they all are in good working condition, but maybe all 3 are flaky?!

When a Volvo shop replaced the MAF 2 mos. ago, they checked fuel pressure, ecu, engine sensors, looked for vacuum leaks and found nothing unusual.

What am I missing here?

Chris
'93 945T 191K