Hi all,

For about a month I've been trying to figure out my P004 ( and sometimes P0300), cylinder 4 misfire code. Done a lot of research and tried some fixes. It doesnt happen all the time, but when it does the engine runs rough only at idle. Here is some history:

Truck has 127k miles
Head gaskets done at 109k
CPS done at 118k
Always use 91+ octane
Bosch platinum +4s installed at 117k
Magnacor 8mm wires installed at around 65k
O2's replaced around 100k

What i have done or know since code appeared:

Replaced plugs with NGK Platinum (old plugs looked fine)
Ran a bottle of Techtron
Checked compression...175 psi in cylinder 4
No fluid loss
Went on a 400 mile round trip last week with no issues. Got home yesterday and went to move the car after an hour of sitting and threw the code. Running with no issues today.

I am leaning towards the coil pack, but before i pull the trigger i wanted to get opinions or suggestions from the experts. One question i had was how long should wire sets last? I cant imagine the magnacors are only good for 60k.

 

Hope you kept those old plugs, they are good and weren't the problem sence you still have the issue.
Go out at night with a water /squirt bottle full of water, open the hood, start the engine and spray the crap out of that wire, from the plug to the coil, if you see a spark, you have a bad plug wire, if not then either it is the coil, carboned valve or flat lobe on your cam.