Hello,

I have a 1990 Volvo 240 wagon that is misbehaving. When I drive the car for an extended period of time the car starts to backfire, stall at lights and hesitate when I accelerate. Eventually the car stalls completely and will not start. If I leave the car for an hour or so and try to start the car again it fires right up behaves normally again until I drive for a bit then the symptoms return. AC seems to aggravate the situation.

The car seems to develop this problem about every two years. At which point I send it to the shop and have any number of items replaced at a significant cost until the problem seems fixed -- this usually takes the mechanic about three attempts -- after each visit I am assured the problem is fixed. I have had the fuel pump replaced, the air mass meter, spark plug wires, O2 sensor and spark plugs replaced. The last time the car had this system, the mechanic said that the problem was a wiring harness.

Anyone one have any ideas as to what the underlying problem might be? What I don't understand is why the symptom keeps returning every couple years or so and why the problem is diagnosed differently each time.

I'm also curious why the problem happens when one might expect the car is hot. The temp gauge is not indicating that the motor is hot.

The car has about 165,000 miles on it. I live in New York City so I don't drive it too much. The symptoms always develop in the Spring when I start to us the AC. I've never had the problem happen in the winter.