I inherited a free 2010 Chevy Cobalt L from a friend a month ago. It has 108,000 miles and so far the only service I've had done is an oil change and a valve had to be replaced in the transmission.
Since then it runs great, the mechanic even told me the car was in good condition and it had been serviced regularly.
That takes me to last week:
After a fill up of gas, the car was idling strange and the "yellow engine light came on" so I took it in since it was due for an oil change. The mechanic said it could be some bad gas or if I didn't tighten the gas cap correctly. Upon examination, the gas cap really was bad, stripped and not sealing correctly. So, I went to Auto Zone and bought a replacement gas cap. As soon as I replaced the cap, the car seemed to idle much better and the engine light went off. The guy at Chevy also told me to ad some "Octane Booster" since the gas could have a bit of moisture in it.
I bought a bottle, added it and the car very quickly improved.
Fast forward to today:
Again yesterday I bought some cheap gas and filled up, no problems until this morning. On the way back and forth doing errands it was fine. Then, as I left for Wal-Mart, it began to idle even worse than before. It was "lurching" a bit and acting like it wanted to stall, only when idling. Since then I went to Wal-mart, shut it off, went in and completed my errands. Upon leaving, it was idling fine, purring and nice and quiet, however, the "yellow engine light" is back on and has been staying on.
I'm going to monitor it and see if it doesn't go off. So, not sure if anyone has any ideas or has experienced anything similar" I wondered at first if maybe a plug wire or plug was or is going bad, because it was "missing" a little. However, no I'm just wondering if it could be some crappy gas that has moisture in it. However, now it seems like it's idling as it should.....this is really weird