Well I finally got my car back after it sat at the mechanics for over a week. They were unable to find anything conclusive since it, of course, ran fine for them. Well I have had it two days now and it continues to stall once it is warm.

After reading around on the forum I thought I would try a few options. First, I applied hot sink grease behind the power stage. I took it for a run and it was still stalling. Next I removed the rs relay and inspected it with a magnifying glass - still nothing noticeable, though I'm still going to order a new one tonight, since they're cheap. There were some signs of erosion on one of the prongs on the rs relay also (a light brown goo). Well, I went at it with sand paper and removed what I could see.

Next, I started the car and it ran fine and longer than it has in the last month. I drove it for about 15 minutes before it stalled at a stop sign. It stalled once again about 10 minutes later, but seemed to be driving smoother. I stopped the car for about 15 minutes then started it up again and it almost immediately gave me some problems. I got it started in a parking lot and jumped out and started moving the power stage around, and it seemed to cut out as I did so. I tried this a couple of times and it was consistent. So, I removed it once again and scraped off a similar brownish substance from one of the prongs on the power stage. Afterwards, it drove home fine, only dipping in power once and stalling once in 15 minutes.

I remember reading that there isn't a way to check the power stage, but it seemed to be affected when I moved it around. Maybe just coincidence, but I thought I might put it out there for comment.

I was also wondering if it is necessary to buy the part of the power stage that is connected to the aluminum housing as well as the plug that connects to the wires, or would the former be sufficient. I suppose I ask because there are a few relatively inexpensive ps for sale on ebay right now with just the one part.

Long post again I know...I'm just trying to be as clear as possible as I'm new to the world of Volvo repair, or car repair in general for that matter! Thanks to everyone who has posted so far, and to those who may post in the future.

-Mark