any ideas?

recently my car has been smoking alot and having really really bad gas mileage and every once in awhile it will back fire or if i have it at full throttle and it will have a lot of black smoke coming out the back... i have a 89 civic hatch with a b16a any ideas?? thanks
Tyrell

plugs and plug wires. black smoke is running real rich. lots of smoke if it's white is a blown head gasket. bluish smoke is burning oil. check u'r antifreeze and u'r oil, see if they look milky or full of crappy liquid. check u'r oil level. back fire, poor gasmilage, and black smoke sounds like u got bad -plugs and/or plug wires. just not lighting off. check u'r timing too.

thank you for the ideas... if this makes any diff i was having trouble having it fire on the 3 cylinder so i replaced the distributor cap (msd) sanded off the corrosion that was on the button inside the distribuor cap and noticed on the old distributor cap that the prong for the 3 cylinder was green and not copper like the other ones... then i also replaced the wires with msd wires and the pluges with boshe plat 4 it fixed the problem with the 3 cyclender not firing but now there is the smoking problem.. also my car has a msd igntion system its that silver sports compact one. any ideas of what else i could replace that could be causing the problem thank you
tyrell

i finally fixed it!! :D it was a vacum leak, took me forever to find it but i did so i am happy thanks for the help
tyrell