I have bought a 2002 BA Fairmont Ghia that's done 145,000 km. It is in good overall condition and has a good service history, but has an intermittent transmission problem. It sometimes jerks into gears roughly when changing up, but if I stop the car and put the transmission into park and turn off the engine, and then restart the issue is often fixed. Problem disappears until after another engine stop and restart. There's no rhyme or reason to this. Sometimes shifts are rough from first start-up and drive, and then if it's stopped and restarted it's fine from then on. Or all is good on first start-up then if the car is stopped and then restarted the problem recurs, but not always and vice versa. I have had the 'box serviced and it's reported as good inside. All shift solenoids are in spec, oil and pan clean, no obvious faults internally and no fault codes on computer readout. Transmission specialist suggested most probable cause was intermittent electrical issue. He suggested changing the inhibitor/neutral/park switch, but it didn't fix the problem. Any further suggestions greatly appreciated?
It sounds to me like a fault with the transmission ECU. By turning the engine off and restarting you are rebooting the computer, which suggests it's a fault with the computer.