i need help, i have a 01 mustang 3.8 automatic. when i start my car up it sometimes dies and also when i'm waiting at red light, and when i'm driving it bucks and i'm usually around 45 or 50 mph. i have had the battery and alternater tested. i replaced the TPS sensor and the idle air controle valve but nothing seems to help. wondering if anyone can help me figure this out

 

CEL on?

When was the last time you did a tune up and changed the fuel filter? Did you check for fuel pressure? Vacuum leaks?

If you replaced the TPS and IACV, i would do a base idle reset also.