Ok, did the dreaded spark plug change and after a few hundred miles of smooth driving she started to misfire. Scanned the code this afternoon and seems like the dreaded cylinder 4 has a misfire. Any ideas on what it could be?

 

Check your coil! The boot is known for getting wet and frying the cold! Try swapping 2 and see if the code changed to another cylinder! I it does it the bad coil

 

Sounds logical. Swap like #4 with #5 (easiest to access) and see if that one get a miss. Ok, but lets say for arguement that I do that and still have a miss in cylinder 4 what else could it be? Injector? I am planning on this taking a few hours on Saturday so I don't want to be out of ideas after attempt one.

Thanks!!

 

Also, it only happens up hill if I press the gas down a little to try to keep a constant speed. If I lay the hammer it does fine and if I let off and let it slow a little up the hill it won't do it either.

I was thinking of seafoaming it and burning off all the crap. GOod or bad idea?

 

Sea foam may help try that and run it! After maybe pull that plug! if its no the coil! There is a possibility that the plug was cracked in the porcine area and causing it to miss! I have ran into this on a few vehicles after a plug change! Just try coil thing and seafoam first!

 

Seafoam didn't stop the misfire but the truck runs a lot better.

 

Mine started misfiring yesterday and it ended up being the COP was cracked where the connector plugs into the COP. It was shorting out sporadically and misfiring when I would put a load on the engine.

 

Well, looks like my Saturday is full. Take out #4 and see wtf is wrong with it.

 

But I did notice today on the drive to work it did not misfire "as bad". I am thinking it might be the injector now. Maybe I knocked some dust into the hole last time and now the injector is plugged up. I guess I could seafoam it again tonight but not sure seafoaming your truck twice in two days is a good idea.

 

Unless you pulled off the fuel rail I'm guessing that the injector isn't clogged. As soon as you run the engine any debris in the cylinder was probably exported through the exhaust if not completely incinerated. My bet would be that it's a bad COP. For what they cost I would just go ahead and replace it. Be sure to use plenty of dielectric grease though.