I'd been struggling three weekends with my son's 1984 240 (non-turbo gas, LH-Jetronic injection), which was running very roughly and stalling. I could barely keep it running.

The manual suggested lots of things to look at, most of them inaccessible. The last item I checked before I gave up and decided to send it to a Volvo mechanic was the air mass meter. The two resistance measurements suggested by the Haynes manual were well within specs.

However, the tow driver who came to pick it up knows these cars and suggested removing the connector from the air mass meter. Bingo! It started up and ran roughly, but ran.

One visit to the junkyard and $130 later, the problem's fixed. Apparently, the air mass meters can fritz even though the test measurements read OK.

Oh, one other lesson: one of the first things I checked was the coolant temperature sensor, which is buried under the intake manifold, in a location that allows for one hand to reach in, awkwardly, but not get enough grip to depress the wire latch and pull it both. I struggled with that for over an hour before I found that I could put some mid-sized water pump (aka Channellock) pliers on it gently, grab those with my left hand, reach in with my right hand to depress the catch, and yank (with the left hand).