2006 Monte Carlo SS P0300

[MarkWilliams64]

2006 Monte Carlo SS
5.3L V8 with 86k Miles

This car doesn't get driven much.
Had ~ 1/8 tank of gas.
I drove it to gas station to fill up.
Put Premium Gas in it.
On the way back home 3miles Check Engine Light came on then started flashing.
It read P0300.

I am assuming the fuel in the tank went bad, most likely from moiture.
I put fuel injector cleaner in it, Techron.

It does seem to idle rough when first starting up but after Engine is Warm it appears to run normally.

Randomly the Check Engine Light will flash, sometimes it will stay on.

Looking for suggestions of what to look for and or do.

[aleekat]

Add some Heet.

[maxwedge]

That code is random misfire. Many things can cause this, usually fuel quality is not an issue unless it is badly contaminated or the fuel pressure is low. A full scan may be in order here. I assume the plugs have been replaced by now.

[MarkWilliams64]

Car was bought used and had been driven very little.
Was wondering about the plugs, as well.
Honestly, don't know the maintenance history.

I'll pull the front side and check them.

Thanks for the info on the Fuel Quality