ok well, i gave my old stang to my mom when i bought my new one. This is a 1999 GT with 67k miles on it. Service engine soon light is on, plugged in my diablo reads random misfire. At idle sometimes at traffic lights it will shut off. She claims going down the highway once, it shut off. So i bought and changedthe coils and spark plugs. still has the same problem. she needs to pass emissions and already failed once. what can i do?

 

check your fuel pressure for fuel pump issues, and the operation of your fuel pressure sensor.

 

I had a similar issue with no codes. I checked the fuel pressure with a gauge at the fuel rail and it read 25 psi. I checked the fuel pressure with the engine scan tool and it read 40 psi?

Which one is correct ?