Need to know if I need to change coil pack or plugs?
I own a 2007 Chevy Cobalt and it idles rough, sometimes even stalling out. The check engine flashes off and on. Two of the 12 codes were P0300 and P0302. They are misfires on cylinder 2 and random misfires. Other codes are P0102; Mass Air Flow. P0121; Throttle Pedal Position Sensor and P0230; Fuel Pump Primary Circuit Malfunction.
I'd start by cleaning the MAF sensor using MAF cleaner, then clear the codes and see if that helps. Often times the misfire is because the engine is not accurately measuring the amount of air inside, the cylinder gets too hot and detonates early. After that, check your plugs, it's always nice to get a new set once in a while so this could be a good opportunity. One thing you can do to check the coils, (if they're the removable kind) is to swap the offending oil to another cylinder. If you get the misfire code on the new cylinder you know the coil is bad. I think the fuel pump and throttle will sort themselves out after this but if they don't, you may want to check the electricals on the fuel pump and then go from there.
If it has over 100,000 miles, change the spark plugs.
Coils are not that expensive to replace.
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