I have a 2006 hhr and in cold weather it will start just fine and after warming it up for a little bit it will drive but once I have to stop at a stop sign or stop light the rpms will fluctuate a little and then the car will die. I've had it into two mechanics and they can't pinpoint exactly what is causing this so they cleaned the mass air flow sensor and replaced the throttle body actuator...it still dies but every time it starts right back up. What else could it be???

 

Have you been able to rule out a bad tank of gas?

 

Yes...it's an ongoing problem it only happens in cold weather...it started happening last winter and it's still happening...last winter I did fuel treatments and heet...all fluid levels are normal and changed on schedule

 

have you checked the plugs or changed them?, good luck.

 

so when you hit the brake it turns off...could a be some kind of vacuum leak in the brake booster?

id have to see it to actually diagnose it...but the brake booster seems like it could do that if the leak was big enough