Ive been getting a p0305 misfire code for awhile now, but it started as a p0307 and once its given me a p0300 code. Ive swapped the COPs around, injectors, plugs (brand new, .045 gap). Ive even changed out the driver side upstream o2 sensor since thats the bank thats been giving me all the issues. So far it seems to be cylinder 5 thats throwing the code the most, its the only one for about 2 weeks now that has. Ive used a noid light to check the circut, spark tester to test the coil, compression is at 150 on all cylinders. There is no water in the plug wells, plugs look normal for only having a few k miles on em. Im at a total loss as to what to try next. Truck is a 2009 FX4 SCrew with 115000k miles on it. Any ideas would be appreciated, thank you

Kyle

 

Sounds like you've done a decent job ruling out the ignition system. If good compression you probably don't have a timing or valve problem. Have you checked your fuel pressures, or how fast pressure bleeds down with the engine off?

You may have a bad injector on number 7.

 

hmm, hadnt considered the fuel pressure, ive seen testers for that, i might go pick one up and give it a shot. The #7 misfire hasnt shown up in awhile, its been #5 steadily for all of the tests so maybe 7 was a fluke.
Sigh, maybe its just time to take it to a mechanic

 

cam phaser - time to tear it apart
did you replace your COP's? if not you might have just moved the problem

 

This is my thought as well. Additionally, were the COP boots inspected for cracks or excessive brittleness? Any chance that a COP wire has chaffed through as thin as it is? Throwing darts at a blank wall here.

 

COP boots are all in really good shape, no moisture, cracks or any of that. Actually they look brand new. Ive moved the COPs all over the truck, replaced em with a set from a friends truck, same cylinder misfire.

The truck doesnt have any of the cam phaser symptoms, but at this point im not going to rule anything out.

Strangely enough on a whim i pulled the O2 sensor from the passenger side, and it looks toast, so im going to put a new one there (its over 100k miles, so they need to be changed anyway) and see what happens.