2003 350Z with 88,000 miles.

The car sat for about 10 days. When I started it, it ran rough, then threw a P0300 code. I cleaned the MAF sensor to no improvement. I use NDSII software (http://home.exetel.com.au/nds/NDSII/index.php) which allowed me to kill one cylinder at a time and when I did so on #3 there was no difference. So I removed the #3 coil pack and plug and they tested good for spark. Re-installed, cleared the code, ran great! For about 15 minutes. On a re-start I got the misfire again and on the way home it threw P0300 and P0303.

I'm not sure where to go next and would greatly appreciate some direction.

TIA.

Swap the pack from cylinder 3 into another cylinder and see if you get a different P030_ code. That'll might give you an idea if it's an issue with that pack or that cylinder.

FWIW, when I had a misfire code last year (P0304) it ended up being a bad seal in a plug well. Unfortunately, Nissan has incorporated the well seals into the valve covers so, although I've seen a couple of refit kits out there, it's far easier to just replace the entire cover. And, if you're doing one you might as well do them both.

Let us know what you find out!

Would there be any other indication of a cover seal failure? The coil pack and plug were clean and dry. Also, I got a spark from the offending plug/pack.

I'll try the swap and let you know.

Thanks!

My issue was pretty obvious, everything was filthy.

I still got intermittent misfires until I replaced the pack, it was toast from all the abuse it had taken.