ok first i unintentionally ran out of gas due to a faulty gauge went to a mechanic because i didnt know it was out of gas they changed the cap and rotor and also put new spark plugs in and obviosly it didnt fix the problem eventually they put gas in the car and it fired right up but now the idle is surging and a ton of black smoke is coming out all they can tell me is that its running rich and they dont know what is wrong there isnt any diagnostic lights coming on in the dash but before occasionally the o2 light would come on so my question is what should i look to replace?could it be a bad o2 sensor? my car is getting plenty of spark and never smoked a bit before this could it be clogged injectors?and if so would it make it run rich? im really confused any help would be much appreciated ohh yea the car seems to run fine at higher rpms if that means anything thank you for your help