2002Legecy

I was having same problem of intermittent CEL along with periodic hesitation and backfiring when climbing a hill in high gear or other situations where power is needed but engine at low RPM. I tried knock sensor but got no improvement. Error codes (I went back a couple times as CEL would go on/off/on/etc) from Auto zone included Cyl #3 not firing. I changed plug in #3 where I found a spark trail going along outside of porcelain. (I changed #1 also while I had that side opened up). The new plug worked - - - but only for several days. I was puzzled and drove around for a few weeks and learned to pull auto tranny into 2nd gear whenever hesitation started as it drove fine at higher RPM. When code said #3 again I changed harness wire #3 (& #1) and it seems to be good but I'm only on my 2nd day & so I have my fingers crossed! (Note: Again #3 plug showed the same spark trail on porcelain as when I changed plug b4, but this time I didn't change the plug.)