Many of you help me try and solve my issues. I tried everything and threw many parts at the problem. I finally gave up and went to a Volvo specialist. Here is the outcome-

1. Surging and high idle- it was a mechanical issue with my TB. The spring in the flap as well as the cable spool were not always returning correctly. The mechanic had a parts car and put another TB on at it was perfect.

2. Bogging and backfiring- He went threw everything you guys suggested. He finally was at wits end and put the whole intake assembly from the parts car and it ran perfectly. Lots of power. It turned out that my injectors were bad, mostly the electronics of them. They were staying open too long intermittantly or all the time in some instances. He said the spray pattern wasn't too good either. They were aftermarket ones that had been put on years ago.

Word to the wise- my brand new IAC valve was sticking and acting up. He put the parts car one on there and it was fine. He greatly cautioned about using non OEM parts. The one I bought was a good offbrand from FCP. He said the aftermarket injectors are not good.

I was beginning to give up but I am glad he stuck with it. He had the luxury of having several parts cars around to diagnose, that's what makes a huge difference.

He also put new rubber in the suspension and man the car drives like new now. You don't realize how many rattles you put up with gradually.

Thank you guys for all of your help.

One more thing- My last name is Rice, I use Rice240 on several Volvo forums and people thought I am "ricing" out my car. I didn't know that was thing. I used to get weird questions from young people and now I know!

https://www.brickboard.com/RWD/volvo/1683374/220/240/260/280/blipping_thottle_get_idle.html
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Art Benstein near Baltimore

At 53 replies, I think you can take credit for one of the longest threads here in recent memory. I’m glad your mechanic helped sort things out. You had multiple problems, some seemingly not common, which always makes it interesting for the rest of us.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now