My 03' 2.4L engine accord has been occasionally idling rough but would always smooth out. That'd been going on for about a month or so. But yesterday it got much worse and I had to park it. Plugged in my cheap Hyper Tough code reader and got P0304, P0303, and P0300. I tried swapping the the coils from #3 and #4 with #1 and #2, but surprisingly the misfires did not follow the coils and remained at #3 and #4. I guessed this could be because my code reader is the cheapest one to be owned. I then replaced all spark plugs with Autolite APP5224 spark plugs and this didn't help. While idling I unplugged each coil pack and #4 didn't make any difference, so I assumed that was my bad pack. I replaced with a new one and that did not help either. I ended up replacing another pack, so now I've got all new plugs and two new coil packs, AND I used a multimeter to check the wiring harness and the problem is just as bad if not worse. Also, I noticed it is now smoking considerably. It was not doing that before I changed all that. BTW I checked the spark plug gap and made sure all were the required .044". So, now I'm not sure what to do! Could this be an air leak? Could the spark plugs just be crappy? I'm obviously no mechanic, so what I've done is about all I know how to do. Right now replacing the spark plugs with a different brand seems like the most obvious thing, but again, I don't know. Any help would be greatly appreciated! Thanks!

 

I'm still thinking coils.

 

So you're thinking I should go ahead and replace the other two coils as well?
I checked them out with a multimeter and they are good according to that.

 

The coils seem to consistently be the weak link when it comes to J-Series ignition issues.

 

Mine is the 2.4L, 4-cylinder engine. That's considered a K-series isn't it? If so, is what you're saying about the coils consistently being the weak link true with these engines as well? BTW thank you for replying!

 

Sorry, my bad, I'd forgotten your engine model. Regardless, Honda engines seem to consume coils as a matter of course.

 

Ok. I'm going to replace the other two ignition coils and report back. Thanks!