Pretty sure its a 02 sensor or coil packs trust me i changed everything on this 2000 cadillac deville dhs even ran out of money until monday then its gonna be 02 sensor and coil packs i got a built in code reader on my car and the code thats poppn up is P0300 and P0440 which is evap systems and misfire and that could be 02 sensor egr valve or the catalytic converter it says i had to go to autozone to get the p0440 code to pop up our dashboard wont give us to much info so i took it to autozone check your fuel filter first then try 02 sensors then fuel pump then coil packs which for my car are fukn 300 each ridiculous