I have a 2000 Hyundai Elantra, 111500 miles on it, automatic transmission. The car is shutting off without reason. Recent work on the car has been: replacing the tailpipe, changing both oxygen sensors (before and after the catalytic converter), fixing an oil gasket leak, and replacing spark plugs. I added fuel injector cleaner which worked for a little while and then it started all over again. Just recently, the car shut off while going up a hill. The car tends to shut off when standing still, but it's not always the case. The only thing that I could think it could be is the fuel filter. I know it's time for a tuneup, but is there anything else that I can consider looking at? Thank you.

 

Just an update:I did get two Check Engine codes. The first one was P1128, and the second was P0734 (4th gear ratio incorrect). I don't know what P1128 is, and as for the second one, I'll keep driving the car until the transmission falls out (which could be any time), or I get another car (whenever that is).