06 Cobalt Occasional No Crank No Start
 

Hi everyone,
My Cobalt has become so unreliable I am afraid to drive it. Her newest game is no crank on starting. Nothing. No sound at all. Or she will rough start and die seconds later.
She has left me stranded on the road several times. I now take my bicycle with in the back seat after having to call a tow truck to take it my mechanic.
He put in a new starter (twice) and replaced both
O2 sensors. The very afternoon I got her from him she did the exact same thing! (Which is explains the second starter. He thought the first may be defective). The battery is pretty new as is the serpentine belt. I have checked fuses and wires as well as ground cables.
My mechanic is stumped and I am broke and so frustrated.
have any of you seen this?
Please help

First of all an O2 sensor only deals with emissions, not running. No crank, does the radio time reset when you have nothing when you try to crank it? If so, you have a battery (or other electrical) connection issue. What DTC does your mechanic have? That's diagnostic trouble codes, I assume the O2 sensors were replaced because of a code.

Hi Kevin,
Yes, O2 sensors were codes. No other ones.
Sometimes there is no crank at all. Others it sounds like I am trashing my flywheel. Mechanic said flywheel is OK. Key does get stuck in ignition sometimes even after recall fix.
When she does finally start she runs great. But I never know when or if she will. Could the ignition switch itself not have enough voltage?
Today she started this morning and when coming home I turned the key and all lights came on. Everything seemed fine. Then the horrible thud of what sounds like metal on metal and no start. Finally after a half hour or so she started and stalled. Then finally started and I drove straight home.
Time for a new mechanic I think.