Misfire in cyl #4
2003 Mach 1. K&N drop-in, Bassani catted X-pipe, Magnaflow cat-back system.
I noticed the car was hesitating and bogging under load, then about 60 miles later, the SES light came on.
I started by pulling the codes P0304 and P0316. I then read a few threads and decided to join the forum, so thanks for having me.
I checked the spark plug and it looks fine as it should, considering I replaced it about 15,000 miles ago. The coil itself also looked fine.
I swapped the coils from cylinder 4 and cylinder 1 and cleared the code. I then started the car and it seemed wayyyyyy better right off the bat. No bogging, rough idle, or hesitation as I pulled away for the test drive.
I let it get about half way to operating temp and floored it in 1st. There was a pretty big hesitation, then a loud backfire, then the car rocketed forward with no hesitation and a nice smooth rev all the way to 6,500 rpm. I shifted to 2nd and floored it again but then there was a slight bit of hesitation through the powerband so I backed off. I drove until the engine reached operating temp then floored it from 1st through 3rd. The car is honestly running wayyyyy better than it was before I switched the coils, but still not perfect. There's still some slight hesitation and a bit of power loss.
Now I'm just waiting to see if when the light comes back on it will throw a "P0301" instead of "P0304".
Does anybody have any other suggestions to troubleshoot this? What's peculiar to me is this: Why would switching two coils to opposite locations make such an improvement? If the coil is bad, I'd imagine that the problem would persist just the same. Only the cylinder of the misfire would change.