I've got a few other threads going but nothing has worked. Did complete tuneup. Still misfired. I read up on the plugs I used so I switched them out for ngk's, cel goes out. 2 days later comes back again, same code random misfire #4. I used generic wires so I replaced them with ngk's also. Cel goes out. 2 days later same cel. I looked at the new cap and rotor i had used and noticed the rotor showed corrosion after 750 miles. Swaped cap and rotor out for new ones again. Cel goes out for 2 days then back on. Each time I've read and cleared the codes with a scan tool. I've not ohm'd the injectors but listened to them all and they all sound the same. Today I swapped #3 & #4 injectors and reset the code again. I can feel the mis but it hasn't thrown a code yet. I will add the car had 157000 miles of which 2000 are mine. Previous maintenance is pretty much unknown. I will say when I pulled the fuel rail the injectors look terrible.

 

The injector I'm holding is out of #4.

 

Wow got a code quick this time. Genetic misfire #3 cyl. So it's a bad injector. At least I know the problem now.