I know how to ohm the coils out but have no idea what they should read I’ve been having issues that I thought were transmission related but it was actually a misfire on cylinder 2 so I replaced the coil and plug but the rest of the plugs I’m changing today but I don’t want to change coils if. I don’t have too

I’ve spent a good amount of money on the truck lately and am kinda looking to get things right without breaking the bank hence wanting to test the coils before I buy them, all the plugs are getting changed today either way


I’ve searched and searched and can’t figure out what they should read so sorry I’m sure it’s been answered but I cannot find it

or maybe there’s a better way to test I suppose, I guess I could just crank the truck and measure power at the coil after it’s running.

 

Resistance across the electrical connector terminals should be around .6 to .9 ohms. Yeah, very near zero..... Resistance from one of the electrical connector terminals, to the part that the spark plug sticks into, should be 6-9K ohms. If you have more than two that are out of spec, replace them all. They all live in the exact same environment.

 

I agree with your thinking, however, in the case of the 4.7 where coils can easily be changed. I would only replace wants needed in a situation where money is tight, I would recommend keeping one on hand though, like mentioned, you just never know.

Like on my 3.6 I had a coil drop at 70k miles, drivers bank you need to remove the upper intake to replace so in this situation I would replace all 3, which I did along with all plugs. The other 3 coils are still running strong at 160k miles, and maybe in the original situation it was no the coil at all but rather a plug issue. I don't recal the specifics other then it had a code and obvious misfire(s)

 

If replacing the plugs and one coil fixes the issue, stop and don't spend any more. Remember, you can also swap them around to diagnose. I picked up a few from a junkyard engine which I keep in the glove, but the original coils are still going strong with 343K mi on em.