I thank all of you for your brainstorming and ideas with troubleshooting.

The shop called and told me they speculated the Mass Airflow Sensor was bad. They would disconnect the part when the car was idling and they said the idle would smooth out. I doubted that this would be the fix because when I bought the car 2 years ago, the previous owner gave me 2 spare MAFs. (He was a junkyard dog and gave me 2 boxes of used spares). When the car was acting up, I tried both spare MAFs and the car behaved exactly the same-- hesitation, pinging, rough idle, etc... so I thought it could NO WAY be the MAF/AMM.

The Volvo shop said they did not have the part in house and would have to order it. The shop's plan was very fair-- they'd replace the part and see if it runs better. If yes, I could pick up the car and drive it a few days and report back whether it fixed the problem. If it did, they'd charge me for a new MAF. If not, they'd put my old part back and continue to try to find the problem. Sounded good to me.

The shop called back a few minutes later and told me when they were ordering the new part they found that the wrong MAF was in my car. I couldn't believe this since all 3 of my MAFs had the same part#. My part: 0 280 212 007. Correct part: 0 280 212 016.

Long story short- New correct MAF-- No more hesitation, pinging, dying, missing. Idle is smooth. Runs great! I wish we could have figured this out a long time ago.

Chris
'93 945T 188K