Hey guys, I have a 2002 Saturn LW200, 4cyl. 2.0 litre gas engine. Got it a few months ago from a prent's friend for cheap, and it's in great condition. 96XXX miles, changed the oil 4k ago (will change again when I can scrounge up some money) and also put in a bottle of Gumout system and gas cleaner, new air filter, new front brake pads and discs (they were warped).

Here's the issue, couple days ago I had to go to the store, hadn't used the car in about a week. Started it up, ran fine. After I came out of the store, started it up, and the engine started to stutter while it was running in the parking space. I watched the RPMs, they dip below about 850 and the engine starts to stutter, then it will rev itself back up to about 950 and stop stuttering for a moment, then slowly come back down and start again. I also noticed driving on the way home that I tried to do some quick accelerating and the engine sort of stuttered and had trouble for about a second, then accelerated fine, this only happened one time. My dad thinks it's either bad gas, water in the gas, or maybe a spark plug. Any ideas before I put more GumOut in the gas?

Thanks,
Bodhi Knight