I hope someone has some advice on this problem. We own an 89' 240dl with a b230f engine. It has 140k miles and we love it. The problem is the car stalls intermittantly and I have yet to be able to figure out what the problem is. I am going to give a detailed history of this problem so please bear with me.
My wife drives it to work one morning at the end of fall (beginning of cold weather here). The car loses power and begins to backfire going uphill. She pulls in to Auto Zone and they hook it up to their test machine and say the alternator is bad. I replace the alternator and the problem is better but not fixed (car hesitates through entire driving range but idles fine). I consider the crank position sensor on the bell housing might be faulty and replace it. Now the car idles well and accelerates fine.
One week after this the car acts up again. The car will idle fine, there is no stumbling or any indication of a problem until you hit the gas and then the car has no power and will hardly move. It almost seems like the engine is about ready to die and then the engine will surge and the car will lurch forward and backfire, then the process repeats itself over and over. The kicker is that I can shut the car off then restart it and the problem disappears!
The problem became more frequent and started to appear when driving at highway speed (car suddenly loses power at 55mph). Still idles great and the problem is still resolved by restarting. I take the car to a volvo dealer and they tell me the amm and airbox thermostat are bad. I buy a brand new amm (not remanufactured like they wanted to put in) and thermostat for the airbox (which was faulty) and install them. Problem is unchanged, wallet and head now hurt. Here is a list of what I have replaced over the past year: air box thermostat, both fuel pumps, fuel pump relay, fuel pressure regulator, amm, throttle position sensor, distributor cap, rotor, plugs and wires, alternator, flame trap, crank sensor, and timing belt. I have checked for vaccum leaks, cleaned the trottle body, and there are no error codes stored by the ecu. I hope someone can help with this headache.