I live in n.e.ohio where we have emissions inspections! my f-150 (carbureted 300 c.i.6cyl)won't pass-too much unburned hydrocarbons they say. I think the problem is computer related-the vac. valves that control the smog pump aren't getting the signal to do their thing! the smog pump is supposed to provide the air to finish burning whatever comes out the exhaust-this I know! I checked all the wiring and with the exception of one white wire on top of the right frt wheelwell(which I couldn't find a destination for) everything seems to be in order. anybody got a clue as to what I should do? I can't even get plates for my 4x4 beast-HELP!!!

 

Make sure your egr valve ports are clean an unrestricted with carbon. Make sure you use a vacuum gauge to see if your running between 17-22 hgs of vacuum. Is the exhaust pipe at the rear really sooty with black carbon? If so , your running rich.

 

most of your smog control is operated by vacuum any leaks would cause an issue. another option that you try is advancing your timing just a degree or two giving the fuel a little more time to burn. plus you can lean it out just by adjusting the air fuel mixture on the carb. not enough to make it hard to start but just enough to make it run smoothly at idle.

 

One other big thing to check with these old systems. The intake and exhaust bolted together right under the carb (to heat up the air). They had many, many problems with cracks/leaks that would suck air and create a lean misfire. A spritz of a flammable cleaner will verifiy.