I have changed my plugs, plug wires, coil pack, even an injector, and i can not figure out why it is still misfiring. i keep taking it to auto zone to have them run the codes, and its always the same, misfire in # 3 cylinder, however i checked and double checked everything, still unable to find anything...a little help here guys? would be greatly appreciated! Thanks!

 

po303 is cylinder 3 misfiring. This could be any number of reasons.

1. Bad plug
2. loose plug lead
3. Bad Ignition coil
4. Ignition circuit going bad
5. Injector failing
6. Upstream HO2S have a build up of carbon on them
7. Compression pressure issues
8. Timing belt needs replacement or adjustment.
9. Crankshaft position sensor dirty or failing
10. Air intake dirty of failing
11. MAP Sensor failing
12. Fuel pressure dropped or even have a clogged fuelfilter
13. Crankshaft position sensor circuit and connector failures

Putting 2 and 2 together I would look at the plugs, leads, O2's and check your injectors. Without really being able to see it first hand I am guessing at what would need to be replaced, but with the indications and codes it generally falls into one of the 4 i pointed out.

 

Compression test that cylinder.