My 2001 3.0 started doing this last week, was driving perfect, then instant awful misfire at idle and acceleration / driving, CEL was flashing too, ran like this my entire drive home and the next day. My scanner did indicate misfire at #4 cylinder in my case. Plugs were pretty new, same with plug wires, so was going to check compression when I learned my compression tester doesn’t have an adapter that fits the Ranger 3.0 well, wouldn’t fit down far enough to thread in….
Figured I’d inspect the plugs and wires as that is simple enough. Spark plug looked good, so did the wires, until I started wiggling them at the top of the ignition coil and I got a nasty shock, lol.
Turned out the hose clamp for the heater control valve rubbed through the insulation right there at the plug end on the coil pack. After I got zapped I looked closer and could see arcing from the clamp to the wire end. Re-positioned the clamp and has been running good again. Luckily nothing major in my case.
Check your plugs and wires first since that is an easy thing to do, then compression test as needed and go from there. If the plugs and wires are old enough, maybe just swap them out. I personally hate just swapping parts without knowing if bad for sure, but if it isn’t easy to test or can’t test it properly, sometimes just swapping is easier and at least their new and can rule them out, when the parts are relatively cheap.
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