Ok, I need some help here. Nobody can tell me exactly what is wrong with my 07' cobalt. The idle jumps when I step on the clutch to 3000 RPM and I have to play with the clutch and gas pedal to bring the RPM down to normal to stop so I don't blow my engine. The shop says its misfiring on the 4th cylinder and my o2 sensors are reading bad. I've cleaned my throttle body recently and changed the spark plugs about a year ago. I don't know I'd it's a bad injector or a vacuum leak or just a dirty IDLE AIR CONTROL VALVE. It has about 132000 miles on it and I keep all Maintence up on it regularly. So any insight would be great! Thanks!