Well, I tried to find the original post, but it is late and I am tired. My 93 volvo 240 was suffering from a hunting idle. I did all the usual stuff: cleaned tb, replaced intake hose, cleaned IAC still no resolution.

I finally broke down and took it to a mechanic. After many days he found that the air fuel ratio was off. Once he reset it, it started to run correctly when warm. Still rough when cold. He also found a bad connector to the o2 and fixed this. He also found a bad temp sensor.

I disconnected the battery to reset the computer. Now after running it a few times, the computer figured it out and it now starts and idles perfectly. So I think it was a combination of the air fuel mixture being off and the bad temp sensor causing the problem.

The silver lining is that the garage only charged me about half of what they could of for the hours they worked on the car.