Help with P0300 and P0303 codes

[dewolfen]

My wife's 2004 Explorer NBX CEL came on and she had it scanned. It printed codes P0300 and P0303 - misfire. I replaced the Mass Airflow Sensor, EGR valve, plugs and wires awhile ago. The vehicle had been running good until the CEL came on. Any ideas on what would cause this.

 

[tmaher]

Could be any one of the following. Check the #3 coil first. swap with another cylinder and see if the code changes. If it does, the coil could be bad.

Faulty spark plug or wire
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector
Burned exhaust valve
Faulty catalytic converter(s)
Running out of fuel
Poor compression
Defective

 

[matt0248]

v6 or v8?

 

[rhaynes]

I just went through a little of this myself. I pulled all 8 of the coils. I found that #8 had about an inch of rusty nasty liquid in the bottom of the spark plug hole. I cleaned all of the coil boots and springs and put new dielectric grease on everything. I blew out all the spark plug holes and cleaned up #8 real good. Then put it all back together and so far so good. This is after starting with P0300 random multiple, then took to dealer and they said it is definitely #5 so I replaced #5, then went to autozone and got a P0308. Just an FYI, I put the supposedly bad old #5 back in and it is working fine. I'm hoping that the water came from cleaning bugs off the front of the grill and hood every week when I drive to Arkansas.

 

[rhaynes]

Found a neat website http://easyautodiagnostics.com/index_ford/index_of_articles_1.php
that takes you through testing.