I agree with that.. My friend's 89 245 had lots of problems with starting and bad idling. We replaced and cleaned a lot, and I can tell you what worked.

-Make sure all vacuum hoses are connected and work.
-Take off the entire air intake from the airbox to the throttle body. Including the throttle body. Clean everything you can. Use throttle body cleaner, and DON'T spray the Air Mass Meter. Just wipe off the two screened ends, look and make sure those wires are intact, and don't spray them with anything.
-Spray the Idle Air control valve clean.
-Find and replace the flame trap. Including that S shaped hose.
-New 0^2 Sensor (Bosch) (Optional at this point for you)

That is what I know would help....

What we also did was...

-Fuel Filter (Bosch)
-Brand new OEM tune up. (Plugs copper, wires, cap, OEM Bosch ignition coil)
-Copper/brass ceramic fuses
-New airbox filter
-Cleaned all the major engine grounds including Fuel injection grounds
-Ran some injector cleaner through the gas tank before replacing the O^2 Sensor.

I can't say exactly what did it, but I'm looking at the physical cleaning of the throttle body and Idle air control valve specifically. If you don't want to take the time to do that properly, you may never find the "problem." To clean that is pretty much free. Or 5 bucks if you consider the spray cleaner. 3 bucks for a gasket. Although we cleaned and reused our gasket... So 8 bucks total and you may be good.

Also don't forget to disconnect the battery for at least 5 minutes. That resets the system, and will adjust the computer to the newly cleaned or replaced parts.. A lot of the times, just doing that will take away some of those pesky "check engine" lights.

After all that, his car starts and idles and accelerates like a champ now. No hesitation, or sputtering or problems whatsoever. In this case and in a lot of cases with the old Volvos, maintenance can be the best investment. If the cheapest fix doesn't work, then move on up to more expensive replacement parts. But always consider and attempt the cheapest fixes first. Cheers!