Why did changing coil on my 2005 Ranger 2.3l make little difference? Code P0350

Question

After changing coil the truck idles better but once under load, (over 3000 rpm, into 3rd gear)  it misses. It idles ok and runs ok until the load increases then it idles rough @ about 500 rpm then suddenly idles normal. I do maintenance regular. Plugs and wires have about 40,000 on them. Next move sir?

Answer 1

When you installed the sparkplug any heavy application of di electric grease , adding some but not a heavy amount, For a P0350 you would have a rough idle at idle, It would also set a misfire code, Some of the problem about a P0350 is that it does not have to set the CK ENG LT on. the reason Ford allows that is the fuel management shuts down the fuel to that particular cylinder fuel injector so it stays within non catalytic damaging. P0350 are usually ECM problems. What you have  does not match a P0350 behavior. P0350 occurs at idle not at load, get another Coil pack, it almost as though what you have is faulty. there also the radio capacitor attached to the coil pack they rarely do go out but when it does it mimic what you have disconnect and retest if it improve replace the capacitor.There something about the  behavior recheck sparkplug wire either they are not pushed in, when you push it in you should hear or feel a click, The only thing that can misfire on load are sparkplug wire,