hanburu_juuboku

This is just my opinion so take this with a grain of salt because I am not experienced enough to know how accurate this information is:

I was told that blue smoke usaully means you need a valve job.
Black usually is a sign of a bad fuel mixture or exhaust problems.

I had a sputtering problem just this past month, Honda told me it was a bad distributor; I got a second opinion and I'm glad I did. It turned out to be a clogged catalytic converter. It was pricey to replace, but it really made a difference and it added some power. It turns out the fuel mixture was too high, this can and did ruin a catalytic converter.

A few signs that it may be a bad fuel mixture:
Engine continues to run after you turn off the car.
Black smoke
Sputtering
Idles too low or high
Bad gas mileage
Exhaust may smell like gas

If you start to lack power, especially going uphill, check out the catalytic converter.
It takes a pretty good mechanic to diagnose if it's the converter or not, the guys over at Honda weren't any help. I had to go to a very experienced trusted mechanic to get the problem diagnosed correctly so good luck. I hope this information helps.