Help: P0300 (random misfire)

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!

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

Quote:

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Originally Posted by sammm

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

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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?

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

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.

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.

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.

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

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!