Fuel additives can cause buildup as well. Run a can of seafoam through a vacuum line to clear out some of the buildup. When I had my heads off I was astounded at the amount of buildup in the cylinders. Gained a solid 4 miles per gallon after that job.

 

No those aren't original, they're platinum plugs. Factory is copper. They could have a bunch of miles on them, or whoever put them in didn't gap them properly - can't make a conclusion there. Misfires would cause a dirty plug too. I'd replace those immediately with new properly gapped champion coppers.

 

Seafoam won't hurt, but it probably won't do much good either. I'd save your money and just run some lucas upper cylinder lubricant in the fuel tank - along with a couple full tanks of super. After you do the plugs and get the new fuel in there, pull the battery to reset the computer. I suspect its already made alot of adjustments due to wrong gap, wrong plug, and the resulting build up. I'd drive it like you stole it for a couple hundred miles, that'll help clean out the combustion chambers. It'll probably run like a new truck by the time you're fueling up the 3rd time.

 

On this last tank before I changed the plugs I put a bottle of Lucas injector cleaner in it. I changed them Friday and then took it for a drive. It ran great, better than it had in a while. Went to go this morning and it started having a multiple cylinder misfire again. I put in the copper champion 570 at the right gap. It’s not throwing any other codes.

 

Was going to say check coil packs, but since it's "multiple," I'd be looking at the crankshaft or camshaft sensor. Replace crankshaft sensor first. Don't go AM with these. Also if oil maintenance hasn't been good, it might be due to timing chain issues.

 

Oil has been kept up very well. It changed every 3-5k miles. That’s probably where I was going next was to the crank sensor. Last crank sensor I had to change on my girlfriends car it was completely out and not intermittent. I’ll still give this a try.

 

Put a crank sensor in and put about 8 miles on it. I have no acceleration problems like before but when I'm stopped it has a real rough idle. If I take it out of drive or reverse the roughness goes away and it runs great. Only when I have a load on it and no movement do I have an issue. I also unplugged and replugged in my coils to see if there was a bad connection somewhere.

 

How is your fuel pressure? Lean-burn miss??

 

Pressure is good. I’ve put a gauge to the rail and checked.

 

So much for that thought.

What brand crank sensor? These trucks REALLY don't like the aftermarket sensors.....