decided to put my battery in the car we were selling and buy me a new one.
New battery in - car wouldn't start.
changed old battery back still no start.
changed screen at tank pump.
changed O2 sensor.
tested fuel pump under the car - it works
checked spark plugs.
switched fuel pump relay with fan relay (as per someone's post) still didn't start.
any ideas?

during all this changing the car started a few times but either stalled or wouldn't re-start after stopping.

before all this happened the car would sometimes stall after starting when i put into drive.
one time it stalled while i was driving and started right back up.