A little black appearance can be normal on the spark plug. But a better description is needed to really diagnose any problems you may or may not have. Follow the following link to see which picture matches the appearance of your sparkplugs the best. http://www.centuryperformance.com/spark2.htm Idle fluctuation is totally different then a rough idle. A rough idle in my car was when the entire car shook and rocked back and forth. To determine any problems, describe both the hard starting, and any accelleration problems you have. -Robert vin 6585 --- In dmcnews@xxxx, "Payne" <bpayne@xxxx> wrote: <SNIP> >The plugs are quite black, but still look fairly new. Should I try a new oxygen > sensor? After I start the car in the morning it seems like it's got an > excessive amount of idle fluctuation for a while. I've heard this is > normal, but I'm not sure to what extent. Can running too rich ever foul the > plugs? <SNIP>