Help: P0300 (random misfire)

[GroceryHauler]

My '97 threw a CEL yesterday. What are the "check these first" items? It's only happened once and I haven't yet driven it since.

1. I'm actually running 93 octane. Retarded timing from 14 to 10 after hearing some troublesome noise while under throttle. But I didn't hear anything suspicious at time of CEL. When it was thrown, I was at WOT for a slightly extended time.
2. Replaced spark plugs very recently. Factory NGK, I believe.
3. Wires are Magnecor about 4 or 5 years old. What are the lifetime on these?
4. Replaced intake and exhaust, inclusing O2 sensors, about 150 miles ago. Coincidence? As far as I know there are no intake leaks. Idle's fine.

Thanks for any help!

[sammm]

Did you gap the plugs properly before you installed them? Get some NGK wires while you're at it too.

[GroceryHauler]

Did you gap the plugs properly before you installed them? Get some NGK wires while you're at it too.

Yes but I don't remember to what, plus I was hasty and may have done a poor job. I'll re-gap. NGK > Magnecor or are mine just too old, or both?

[sammm]

^Both. Check your plug gaps for starters since that's what you recently changed.

[Rogue]

P0300 is usually a coil, and the raw fuel will quickly destroy the Cat.
Magnacor are lifetime warranty, but good luck with that.
IMHO, Stock coils are not strong enough to need fancy wires.

[Labora]

I have some spare coils if you want to try swapping a few LMK.

I had random misfire code because my coil plugs on the harness where cracked/dry rotted and broke causing problems. Had to put new ends on those to fix the issue.

[GroceryHauler]

Thanks guys. I guess I'll re-gap and throw on some NGK wires and see what happens. Unless there is a good and easy way to test the coils.

[Rogue]

Clear the code…..BTW, I have a box of coils if it comes back.

[GroceryHauler]

Plugs were fine. Replaced the wires and cleared the code Monday night. So far so good. I did notice for the first time ever what felt like a weird pulsating hesitation (non-linear increasing and decreasing acceleration) in low gear at relatively low RPM (2500 - 4000). The car was mostly cold at the time since I was in a rush; I usually warm it up more before driving. Haven't really noticed it since. Of course, I could be imagining the whole thing. As usual, I'll keep an eye on it. Thanks!