Spark plug resistance comparison

[Nctruckman]

On this chart I showed the readings from motorcraft, Taylor and cheap duralast (AutoZone) wires. I found the high resistance of the duralast wires was causing a very hard to diagnose idle missfire. These readings are in thousands of ohms. I inspected the plugs, no indication of fouling with 270k on the engine, these are only a few years old. Coil pack is new oe ford. Something to consider if you have a weird missfire with no code.

 

[J_C]

The way this is presented is confusing at first.

What I'm getting out of it is:

Taylor 82032 has 75 ohm average
Ford WR6120 6K2 ohm average
Duralast 9K5 ohm average

The thing is, your ignition system ought to be able to handle 9K5 ohms, even 12K ohms. Single-digit Kohm resistance on wires is typical for domestic vehicles, and none of those readings are out of a normal range considering some wires are multiple feet long.

I'm suggesting that the Duralast might just have a break in them or were arcing somewhere because their insulation broke down prematurely.

 

[Nctruckman]

The way this is presented is confusing at first.

What I'm getting out of it is:

Taylor 82032 has 75 ohm average
Ford WR6120 6K2 ohm average
Duralast 9K5 ohm average

The thing is, your ignition system ought to be able to handle 9K5 ohms, even 12K ohms. Single-digit Kohm resistance on wires is typical for domestic vehicles, and none of those readings are out of a normal range considering some wires are multiple feet long.

I'm suggesting that the Duralast might just have a break in them or were arcing somewhere because their insulation broke down prematurely.

Sorry the first two sets I numbered from shortest to longest length. And the last set (AutoZone)I didn't get a chance to. It could be the resistance might of not been the issue but the quality itself, but you really can't measure insulation condition.