Hey there Mike Volvo and welcome to the Brickboard.

Sounds like you have been very thorough. Your car looks great and it is clear you have a lot of respect for the machine. Your work is even beyond what most people here would consider a "zero-mile" service, and you set a great example for what can be done in bringing an old Volvo back to new.

I didn't see in the list what you had done to the IAC, or idle motor. I see it on the bench all cleaned up in a picture. It could still have carbon somewhere in it, or be sticky and require some lubrication. I like using CRC's 6-56 marine lubricant to apply a light oil that doesn't evaporate in parts like this. Seems pretty harmless to electricals as well.

That said, try another one! Get a junkyard IAC along with another MAF, and try the parts for any difference. Even better, try yours in another car with the same family of fuel injection (LH Jetronic 2.4, for automatic cars, 3.1 for most with 5-speeds.)

And I also kind of hate to say this... but they all do that. The 240 and 740 and 940 tends to have a rough idle. The 240 shakes a lot more, because they don't have the hydraulically damped engine mounts of the 700/900. And cheap mounts are not as strong as Volvo ones, for certain. You get what you pay for... Scan Tech is cheap but you will have to do them again in 2-4 years.

I've had 13 240's over the last 13 years, and they've all had some issue with engine vibrations. They just weren't very civilized. My '92 just had a transmission replacement and I'm about to go through a lot of what you're doing, for the second time since I picked it up, to see if some of the roughness can be sorted out.

Good luck with yours!
--Rob
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89 244GL Turbo // 92 244 M47 \\ 90 745T // 76 242 Convertible