How do you check coil packs?

[Timco]

It's on my truck but same setup. I'm doing plugs but want to check those. Rough idle.

Is it good / bad or can you check performance?

[Flavor 987S]

Bad coil packs will show:

CEL
Misfires
Stumbles upon load (up a hill.....or little throttle application)

Just to name a few.

[JFP in PA]

Originally Posted by Timco

It's on my truck but same setup. I'm doing plugs but want to check those. Rough idle.

Is it good / bad or can you check performance?

There is a simple test for the coils to see if they are good or not. All you need is an ohm meter:

Resistance between terminal 1 and terminal 15 at 20°C: 0.3 - 0.7 ohms. Anything outside of this range is suspect.

Likewise on the spark plug connectors: Resistance: approx. 2 k ohms

One potentially misleading issue with static resistance testing: Coils often test fine on the bench, but then break down electrically under hot load conditions. So if the unit is suspect, test it on the bench, but then swap it with a another coil pack from the engine that is working correctly and see if the misfire moves to that cylinder. If it does, the coil pack is toast.

[jcslocum]

Inspect closely for cracks. They are not easy to see so take a long look and use a magnifying glass if you have to.