My truck has a low rpm miss. The computer was tripping random misfire codes as well as cylinders 6 and 7. 120k so I did a tune up. distributor cap, rotor, wires, pcv valve, plugs, wires, air filter. Still missing, but accelerates much better. Still producing general misfire code. Whats the next step. Would change a fuel filter but don't think the truck has one.

 

Fuel filter is in the tank with the pump.

 

Try pulling your injectors and clean them in an ultrasonic bath. If they look really gunked up, get back there and pull the fuel filter and inspect. There's also another piece along the fuel line that gets gunked up (a check valve, regulator, or something, sorry I can't recall the piece right now). But that's another thing to check.

 

One other thing. My spark plugs when I pulled them were ashen. I had Bosch Platinum +4's and the all four terminals were white. Don't know if that will shed any light into the mystery either.

 

Well, I don't know if its your problem, but our engines don't like Bosch +4s.

I use NGKs, several here use Autolites or Champions. I'd recommend Champions or NGKs, seem to have the fewest problems.

 

Well I put champions back in it. But the miss is still there. I think I have a fuel problem whether it be a stopped up line, an injector, or fuel pump or whatever. The truck has had 120k of which I put on the last 70k on it running it on average 70 to 80 to 90 so its about due for some tlc. I just don't know where to begin. Im going to c-foam the hell out of it tomorrow hoping that get me some vast improvement. If not just going to have to break out the checkbook and start replacing some of these systems that i know have to be worn out. Just don't know which one to go with first. They all so damn high