850 turbo intermitent stalls every time when warm. 150,000 miles, all maintenance to date, running perfect until one month ago. Now at local non factory Volvo repair for three weeks. They can not figure it out. Throttle relay replaced, cam sensor, ignition, fuel pressure, plugs, wires all checked OK. Starts perfect, warms up, engine stalls for seconds every minute, whether giving gas, coasting etc. Finally stalls and will not start until cold. Factory Volvo repairman also ran all codes and can not figure it out. Said it will not allow him to even run diagnostic. Local Volvo repairman ready to give up. He mentioned he could try and replace two O2 sensors or computer, but I would have to buy those items to try, and they may not fix the problem. Car is totally unusuable. Any suggestions would be appreciated.

Try disconnecting your MAF sensor and start. If it starts and idle normally you have found the problem. Hope this helps.

I talked to the mechanic. He said
1. The MAF sensor was swapped with good used one and was not the problem.
2. The entire fuel system was checked including pump, relays etc and there are no problems. He drove the car when warm, and while the was stalling the fuel pressure was fine.
3. The cam sensor was checked OK and swapped with a good used one and was not the problem.

He thinks it is significant the Volvo dealer’s diagnostic computer will not scan the car or scroll through the diagnostic pages at all.

Any thoughts would be appreciated.

I would second the MAF sensor and if that didn't prove out I'd swap out the fuel pump relay.