Just came from the auto store with a misfire. Guy said on coil C what the hell does that mean? How do I know which ignition coil is bad? 2005 5.4

 

How many miles are on your truck? You can get a set of 8 coils off eBay shipped for less than 100.00. If your pushing high mileage (100,000+). I'd change all of them for good measure and keep the old ones for down the road. They make hand held tools to check COP's but they are pricey. This probe on Amazon is about $100.00, more than you would spend on a set of coils.
Check your plugs as well. Cracked porcelain can cause misfires. I've had misfires attributed to both. Coils and cracked plugs.

 

Got just over 83k

 

Misfires can be the plug, the coil or the injector. Being that your truck is an 05, and has problematic plugs, I'd suggest reading the sticky at teh top of this forum, and then changing the plugs. At 83K miles, if it hasn't been done, you're overdue.

 

Thank you YouTube truck is fixed. Spark will be changed once I got the money.

 

a good reader should tell what cylinder is misfiring, unless the code is just a random misfire. i know i would get random misfires if i started my truck with ac on. the ac was going out and was putting more strain on the engine i guess and was making it idel low at start up and misfire. but like above posts best to just change them all if you can.