Dodge Repair: Rough idling ect., fuel injector cleaner, stp fuel injector cleaner

Question
I have a 1988 Dodge Aries Series K. I just had an oil change recently. My car now is idling really rough and cuts out while driving. Also i noticed some dark smoke coming from the muffler this morning. Thinking it was spark plugs and air filter we replaced them but the problem is still there same as before. What else could be causing the problem?

Answer
You've probably got fauly fuel injectors, which are either spitting in too much or not enough fuel, which will produce odd colored smoke. Or, they may just be dirty. Try running some STP fuel injector cleaner and a bottle of octane booster in the gas, it might help.