4.6l v8 misses at idle. thought plug wire was bad as i could see arcing along wire at night. Replaced wires still could see arcing along same wire. Suspect coil pack. Checked with multi meter secondary resistence should be between 13-14 ohms. Read 13.49 to 13.50 on 3 of 4 pairs other pair read 12.90. What do you think? Coil pack is $50.00 is it worth the risk? Car seems to run ok just misses at idle and wants to die at stops.

 

if you can see arcing that is pobably what is causing the miss is it acing at the coil or where exactly is it arcing, you already replaced wires did you replace all of them, you might try a new sparkplug on the cylinder it is arcing on before trying a coil and the 4.6 is common for the pcv hose to be leaking vacum and causing a rough idle so you may want to follow your pcv valve hose all the way back to where it hooks onto the intake at both places and make sure its not leaking.

 

Ford has had numerous woes with plug boots on this engine.

Make sure you use a good quality set when doing a wire swap.

 

I replaced all the wires with a new set, at night when you rev engine you can see current running along the same cylinder wire as before. I went back to the parts man and he suggested coil pack may be shorting out. Thats why I checked resistence on coil but I wasn't sure if 12.90 is low enough to cause problem. My manual does say if its not between 13-14 to replace it. But 12.90 is close to 13. It does seem electrical though as the car will idle smooth and all of a sudden start missing as if something is shorting out somewhere. I will check the pcv hose though and thanks for the help.
cman

 

If the coils are the same, try swapping it and see if the problem moves to that cylinder. If it does, you have found your trouble.