It is a 91 302 in a f150. Dealing with for a week or so now. Started vehicle one night ran very rough, reved motor and cleared up. A few miles later started to sputter, reved and cleared agian. For a few days if over 3 to 4000 rpm it would run good. Now though it runs very rough at idle and dies. While driving spits and sputters badly to point it is undrivable. But no smoke out tail pipe.
Things I've done or checked. First temped the exhaust manifold at ports, cyliders 2,6,7 running 150-200 degrees cooler than others. Replaced all plugs, wires, cap and rotor. Timed to 10 btdc. Changed out #6,7 fuel injectors. Replaced fuel filter. Replaced air filter. Checked codes (map and o2 came up) replaced map. At fuel rail checked pressure its good. Unplugged tps and vehicle revved a bit so I guess it is working. Checked vacum to map, has vacum.
Non of these helped. Hoping you all have some advice

 

now have checked o2 sensor, tps, and egr. While running it may run completly smoth for a minute or two then just go back to running on 5 cylinders. Does not matter hot or cold.

HELP ME !!!!!!

 

Sounds to me like checking your exhaust system for restriction might be worth a try. If the converter is stopped up it can cause you a lot of problem and send you on a wild goose chase too.