I ran and OBD2 reader on my car and came back with 5 codes...

P0134- o2 Circuit No Activity Detected (Bank 1, Sensor 1).
P0303- Cylinder 3 misfire detected.
P0440-Evaporative emission system.

These showed up as pending
P0507- Idle Air Control System RPM higher than expected.
P0440-Evaporative emission system.

I bought the car with a blown motor from a person I know and ever since my friend I put the new motor in it has always had a misfire. It use to misfire really bad and we started with taking the injectors off and noticing the o rings were bad. We replaced the o rings at that time and it calmed the misfire down a lot and made the code go away. However, it still always had a slight misfire that has bugged me so I've replaced things trying to correct this. The car got new plugs & boots when we put the motor in (about 2,000 miles ago). I've replaced the fuel filter and have ran sea foam through the system a few times. Still had a misfire. So, my friend DTP and I figured we'd start trading parts on our cars until we determine the problem. We've traded IDI covers & injectors....both off my car work fine on his and mine still misfires on his. I've also had the compression checked on my head and it came back ok. Maybe i'm just a little frustrated with the car but the POS is starting to get on my nerves. Anyone have any ideas on what the problem could be? I've posted the codes my car is reading (and the cylinder 3 misfire just came back) in hopes of getting to the bottom of this. Could the fuel pump have anything to do with this??


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Forgot to add the o2 sensor one was only showing up because a friend of mine recommended to disconnect it to see if it helped the misfire (something to do with an exhaust leak i had before).


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