I have a 1979 with a 400 engine. It will run great with tons of power, very smooth, and sounds very happy and almost as if a switch is flipped it will have no power, tons of hesitation, shoots flames out the carb and after 20 seconds or so its running great again. the exhaust is glowing red hot on both sides very evenly from lower part of manifolds through the cats(one of of each manifold) the change in the way it runs is very distinct and sudden. Its like there's a switch to make it run bad and its being flipped on and off by some gremlin.
Its all stock, has all ca smog goodies, 2 barrel motorcraft carb, electronic ignition(remotely mounted box on fender well). has straight exhaust pipe after cats(one off each manifold)
Just to let you all know this isn't a ford truck, its actually a town car, sorry i just wanted to ask here because it seems like you guys are the smartest group of people around for my problem, but i have a 1993 f250 diesel and love it this site comes up all the time when i search the web for info on my car and is still very helpful
rebuilt the carb thinking sticking float, but inside looked great and it didn't really change anything after i put it all back together. fuel filter is good. new cap, rotor, wires, plugs, and air filter. any advice would be greatly appreciated, thanks

 

Tell us about the red-hot exhaust... is it ALWAYS that way? Or only after it's been running poorly? Or......?

 

the thing is i dont really know because it switches back and fourth from running good to bad so quickly, i dont think the exhaust would have enough time to cool down while it is running good before it runs bad again. I would say that the glowing is related directly to the problem because i used to drive this car everywhere, and was under the hood all the time, also drove over alot of dry grass and never noticed anything. also forgot to mention i am getting it up and running again after sitting in my yard for about 6 months, started right up on the first try tho. had no problem when i parked it there too. thanks in advance guys!

 

i went ahead and bought ignition pick up, ignition control module, and new coil all brand new hoping to throw some money at it and fix it. when i went to pull out the pickup coil i noticed the the stator?(the piece under rotor that gives the pick up a signal) was loose and able to spin freely on the distributor shaft, changed a 5 cent roll pin and it runs like a top, so good that i could drive it back to the auto parts store and get my $200 back for all the parts lol. thanks for the help, great site!

 

Thanks for the follow up! It's easy to learn something new here when these things have a conclusion; especially a good one!