After replacing the coil on cylinder one it started misfiring about four days later?

Hi,

That is a good question. Do me a favor. Switch the new one that appears to be failing with a different coil on the engine. Drive it that way and see if the misfire changes cylinders.

If you switch it with cylinder two and then you get a P0302 (cylinder 2 misfire), the coil is the problem. If the same issue happens as prior (the misfire stays at cylinder 1), we could have a faulty spark plug, a weak connection at the coil connector, low compression in that cylinder, and the list goes on.

Take a look through this link, it explains how to check the system to confirm the proper voltage reaches the coil and how to check if the coil driver is working as designed:

https://www.2carpros.com/articles/how-to-test-an-ignition-system

Let me know what you find.

Take care,

Joe

I tested the wiring with a Noid light. I also checked the spark plug to make sure the gap is correct. I checked fuel injector on cylinder 1 and it seems fine. The only things I haven't done is change coil with a different one and a compression test. I'll check the things you said then let you know what's going on with it. Thanks for the advice.

I would try replacing the spark plug, even though it might look okay I have seen internal defects that are unseen to the naked eye.

Okay. I will change the spark plug with an AC DELCO that's already in there now.

Hi,

Thanks for the update. Let us know what you find. We are interested.

Joe

I just wanted to give you an update. The coil i put on is still holding up just fine with no problem. So I guess the problem was a bad batch of coils from the manufacturer.

Yep, it happens, thanks for letting us know, we are here to help, please use 2CarPros anytime.