My son's 850 stopped running suddenly. The local Volvo dealer changed the plugs and it ran again. It was low on oil. They told me all the engine seals needed replacing and it had a clogged flame out valve.
I could not get the engine to leak oil, so I did not replace the seals. I changed the flame out valve and blew out lines. My son drove the car and the catalytic converter caught on fire. he put it out. I changed the catalytic converter. The car runs fine for about five miles, then runs as if badly flooded. If I change the plugs it runs well for another few miles. but runs bad when it warms up. The dealer insists that this is a clog in the ventalation system. If that were the case it should run bad even when cold. It seems to me to be a sensor that keeps the engine "choked" or injectors open.
Any ideas?