This is for a 1999 with a 5.9. When I got it a week ago, the plugs were shot, the cap and rotor were shot, and I'm assuming the wires too. I replaced all of the above (Advance Auto Parts wires, NGK V-Power plugs gapped to 0.040, Napa OE replacement cap and rotor) and I removed and cleaned the TB and the IAC. The fuel pump was also replaced yesterday as the FPR was shot.

The truck still has this mild miss/shudder, worse when cold, still mildly there when warm. I've tried routing the coil wire away from the spark plug wires (for whatever good that does) but it's lying on the valve cover so I'm not sure what good that'll do. It does have the black plastic looming on it so the wire isn't directly on there, it has that protection.

It's sort of annoying.

One thing that I have noticed is the temp gauge shows about 160ish when the truck is warmed up. I'm thinking that either the previous owner put a lower temp thermostat in it or the thermostat is shot. I don't know that it would affect idling at startup.

I also have Techron and Sea Foam in the gas, and have gone through 3/4 of the tank with it and it hasn't seemed to have helped.

Any suggestions?

 

I don't how good AAP wires are , but if you do a search here, there is a TSB on how to route the SP wires. Try that. And have you checked the plenum gasket?