Encountered bizarre misfire CEL situation

[xt2005bonbon]

Several years ago, I suffered from constant misfires on #2 in my 06 due to a tight exhaust valve. At that time, I was already using BtSsm and was monitoring the misfire pattern. I observed how the CEL would get triggered and when it would go away. I saw that if the misfire count was getting greater than ~30 for a few times in a row, the CEL would turn on. Then, if the misfire count would stay somewhat low (e.g. <10) and the engine would get turned on/off like 5-7 times, the CEL would go off. Now, I am sure the ECU may have been tracking how long the engine was running with low misfire count.

Now, fast forward last month. My wife drove the car. Next day, I took the car and noticed the CEL is on: misfire on #1. Really odd. From that day, I carefully monitored the misfire count on #1: always stayed zero! Nothing. A month has passed, several turn on/turn off cycles, not sure the mileage, but the CEL never went away!! Car kept driving fine, nothing weird. Now, it's been lots of city driving, no long drives. Maybe that's a factor. In any case, got sick of it and finally reset the ECU. Anybody encountered this before?

[Max Capacity]

No, but my guess is a bad spark plug. 

 

Tell us the age of the plugs and coils ? 

 

You do know...these cars like to be driven for distance. Only time my wagon had a miss-fire, was when I knew I was way over the spark plug life. I was pushing 80,000+ miles on the old plugs. 

[xt2005bonbon]

I first thought of coil, not necessarily spark plugs. could be that.

Just checked my logs: last time spark plugs were changed, that was on, wait for it, Sep 2014 @ 127000 miles. I am now at 177K. Coils have not been touched since I've owned the car @ 120000 miles, except #3. Then again though, I always monitor the misfire count almost each time I drive and see nothing on all four. Weird.