2001 Cobalt 246 engine idling real rough

by Mike
(NH)

Cobalt 246

Just got a 2001 Cobalt 246. Was running great when I started today but skipped a couple times and now it is idling real rough. I put high octane fuel in it which I think the previous owner just used regular but marine fuel. I am trailering it so I just stopped in my way up to to the lake. Is it most likely the fuel?