You are correct. All 6 coils do not go bad at the same time. Plus, there are no codes for just the coil unless they are circuit codes.
If you have misfires on all cylinders, then we need to check the things that affect all cylinders which are air and fuel.
If you changed the plugs and the light went off and then came back on, I suspect the plugs are fouled and replacing them got the engine running well again. Now they are starting to foul again.
This means we need to start with checking for a vacuum leak and then the fuel pressure.
Here are guides that will help with doing both of these:
https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge
https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator
Basically, we need to find out what both of these systems are doing and then pull the plugs again.
Here is a chart that will help with finding out if the plugs are fouled or not.
Please run through this info and let us know what you find.
Thanks
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Thursday, December 23rd, 2021 AT 3:45 PM