Excessive Carbon on Spark Plugs
 

I took my baby in to the dealer for her first oil change today. I mentioned to the mechanic the car idles a little rough in a cyclical fashion (smooth for a sec, rough for a sec, smooth for a sec...). I've seen a few people comment about that problem before. Some fixed it with lower octane fuel, some just accept it as the nature of the beast.
My mechanic said there was excessive carbon build up on the spark plugs so he replaced them to see if it's the problem. The car is a lot smoother now, but I can still feel the idle just a little bit.
Has anyone else been down this path? What could cause so much carbon in under 4000 miles? I've always been using 91/93 octane, sometime V-Power, sometimes Hess.
Thanks for any advice!

Ur drivin it like granny, thats y the carbon build up. U got to burn it off man

Yup, this is what I heard from long-time rotary owners too. You drive it like a granny, you pay the price. I hope your problem doesn't come back.

It is a good maintenance procedure to drive your engine up to 9000 rpm once in a while. Just do it when there's a wide stretch up ahead in the freeway. Don't worry, it's suppose to go that high--it was made to do that.

Hope you're not boggin around town @ 2500 rpm in 6th gear. I try to cruize in the 3250 - 3750 rpm range and get good gas mileage (avg 18 - 19 mpg, 50/50) and never a single problem in 10K miles. At least a few good white knuckle 9000+ shifts per day and 93 octane helps keep the carbon away!