Tune Up?

[90gmcmoneypit]

I have a 1999 Montero Sport that I put a LOT of highway miles on. Roughly 1000 a week.

Regular driving conditions it runs smooth, great at idle, decent on gas, ect. But generally after I put about 4-600 miles on it at one time I've noticed a problem.

I'll shut the truck off and let it sit overnight after my long weekly drive. At that time, it'll be running fine.

The next morning, however, I'll notice a rough idle. Usually it will clear up after a couple of miles and be a non issue, but occasionally my SES light will pop on.

The code I'm getting is no spark in cylinder 1. But after a while the idle will level itself out, I'll reset the computer by disconnecting the battery cable and the code will clear.

I'm assuming this is probably a bad plug, wire, or cap, but I'm just wondering if anyone has some feedback or a possible solution. I'm considering running some seafoam through the system or some injector cleaner to see if that maybe clears it up, as changing the plugs looks like not so much of an enjoyable task.