I am new to this site and have been looking on the internet for a while and was wondering, besides being spark plugs and wires and/or a bad coil pack, what other things could make it so i have misfires on cylinders 4 and 6? going to replace the plugs and wires later today when they get to my house but i just want to know what other things i could be so i can evaluate the potential repair cost and should the wires for cylinders 4,5, and 6 be under or over the intake manifold? i bought my truck used and they are currently under the manifold i think it would make more sense to have them over personally.

I have a 1997 Ranger 4WD with the 6 cylinder 4.0L engine.

I can't remember the codes that it tripped at the moment but i think one might have been the 304 code not sure though.

Update: i tripped the 300,304, and 306 code but don't know about any others i remembered what codes i tripped the other day when i had it scanned

 

I have changed my wires and plugs and it runs a lot better than it did before but it's still misfiring so i am thinking maybe bad coil pack?

 

A number, or combination of things can cause a misfire, like plugs, wires, coilpack, dirty, faulty fuel injectors, electrical connections to them, sticking or worn valves, messed up fuel trim from a dirty MAF sensor, clogged fuel filter, weak fuel pump, lazy O2 sensors, even low under load battery voltage & the list goes on & on, so have the computer scanned again & post All trouble code Numbers found, as they can provide good trouble shooting clues.

Don't throw parts at the problem on a hunch, take the time to do a proper trouble shoot, get a positive result, Then replace the problem part.

If you've come to suspect the coilpack & think its case may be cracked underneath, which its known to do, raise it on an insulator to see if the miss clears up, or with it raised, idle the engine at night & maybe spritz it with a spray bottle of water, while looking & listening for arcs & sparks, or a rougher idle, if no joy & you come to suspect the coilpack may have internal electrical break down, most autoparts stores can/will bench check its output at no cost.

Edit: Some additional thoughts, P0300 is a random misfire code, P0304 & P0306 are for cyl 4 & 6, which don't share coils in our waste spark coilpack, as in the coilpack, cyl 4 is paired with cyl 3 & cyl 6 is paired with cyl 2 & the plugs are fired on Every rotation of the crank shaft, once on the cyls power stroke, then again on its exhaust stroke (waste spark).
If your store can't do an output test on the coilpack & you still suspect spark, disable the fuel pump so the engine won't run & the injectors won't wash the cyl walls down, as you crank the engine while using a spark tester on plug wires 4 & 6, to see if you have a good quality hot spark at max specified gap. The spark should snap with authority & be blue white in color, not a wimpy snap or yellow color.

Some thoughts for consideration. Let us know what you find.

 

Taking it out to my cousin's garage on monday because i have to get my valve cover gaskets replaced. I am leaking oil pretty badly so i am just going to have him scan it and fix my misfire hopefully.

 

If its leaked oil onto the plug wires, that could cause mischief.

 

according to the computer and my cousin my misfires were fixed when I changed the plugs and wires and the valve cover gasket wasn't bad the valve cover itself was loose so i tightened that up and now she's running like a champ thanks guys for the ideas.

 

OK, good find, fix, feedback & to hear it seems to be running well. Thanks for closing out your thread.

 

so uh, the problem is back threw the same codes p0304 and p0306 and did a voltage check on the coil pack the ones for 4 and 6 are a really low voltage and are causing the misfire and i checked the electrical plug that plugs into and it's getting a full compliment so going to replace the coil pack tomorrow and see if that fixes it.

 

Most autoparts stores can bench test the coilpack for output before you spend your gold for a new one.

 

My cousin and I tested it and that's what we found replaced it and she runs better than before.

 

OK, good feedback & to hear you think its fixed again!!!!