08 MCSa with one weeks worth of uneven (low RPM) idle that occurs once the engine warms up. No performance difference noted. CEL came on after several days and has stayed on. Vehicle has 19K miles.
Starts normally, but several miles later on the AM commute, it's hard to wait at red lights as the idle is in the 400 to 700 rpm range with the car hopping up and down as you sit on the brake pedal. As you leave the light, it seems to straighten out by 2200 rpm.
Once you are on the interstate, all is well. Gas mileage is the usual, minimal soot on the exhaust tips. Rotten egg smell is quite prominent if you let it idle in the garage.
Any ideas? Going in for service this Saturday.

 

That smell usually indicates your catalytic converter is working properly and that your local gas has a high amount of sulfur content which is usually removed at the refinery.Try another brand of gas.

 

just curious, what octane gas do you use, and what brand?

 

Always use Mobil 93 Octane...

 

Maybe try Shell. My understanding is that each brand of gasoline has it's own additives, and not all additives work well on all engines. It's possible the Mobil additives give Minis heartburn.