I have cylinder #8 misfire, the spark plugs and wires have less than 10k miles on them. Lose of power, don't know where to start. Please help, thanks.

 

Swap the #8 spark plug to its opposite cylinder (#7) and clear code. If it comes back as at number #7. its the spark plug. If it comes back at #8, it swap the spark plug wire, clear code and drive. If its comes at #7 its wire. If it comes back at number #8, it MAY be the coil.

 

is there a way to test the coil, other than replacing it.

 

baby steps

 

Yea, there is a ton. But do you really want me to write all that.
Personally, the cars I work with are coil on plug, so I swap em with a known good cylinder. . For these trucks, I'm not swapping a coil. If there is reason to suspect its bad and it comes out, its getting changed.

But Like Drowssap says, baby steps. Work thru the steps.

 

I was having a #8 misfire. Turns out my intake hose from the MAF into the intake had worked its way loose. Air was getting in past the MAF throwing off the firing. Once I tightened up all the intake hoses - code went away. I also cleaned the MAF, IAC valve and checked all the plugs and wires. I also had one cracked plug on the ceramic. Replaced that. On top of that I ran SeaFoam in the fuel just in case an injector had something going on.

The major problem was the hose being loose. Made a huge difference. The other stuff I cleaned was mainly to smooth out the idle. Physically grab the air intake hoses and wiggle them to check for looseness.

 

My money's on the plug wire. I've had even fairly new ones go bad, sometimes due to rough handling of the boot during installation. You might also try watching the engine at idle in the dark to look for any arcing.

I think it's correct that a failed or failing coil is more likely to trigger misfires on ether two or four cylinders, but not just one given the wasted-spark system used on the DII. In addition DII coils fail only rarely, according to P.T. Schram.

 

My challenge with "swapping the plug wire" was that even lifting up the SAI bar out of the way, there was no way for me to simply "swap the wire". Even using tools, the wire was in the coil so tightly that I felt I would destroy the wire getting it out.

For my truck, swapping even the top #5 or #8 wires involve removing the plenum. If I do that, I'm buying a new set of Kingsbourne wires and just replacing the suspect wires. Even though my wires are less than 6 months old.

 

I keep forgetting so many of you guys have SAI.

 

One day I may actually find out what SAI means and the thing actually does. I was guessing something like Secondary Air Intake. Other than that, it means, "bar someone put in my way just to be annoying". :-)