1079 f150 weird problem...

Your truck is over 900 years old, it is bound to have a few weird problems.....

I couldn't resist. Sorry

 

A lot of folks are giving you some great advice. However, if I were you I would start with the basics. Your engine needs compression, fuel, and a spark to run. To start, check your compression, make sure that you have compression in every hole. I did a tune up once on my old 460 that ran great for a week then started missing horribly. I scratched my head, checked and rechecked wires, wondered what the heck happened to the carb, and after hours and hours of messing around, I finally checked the compression. Guess what I found? A dead hole that was caused by a broken valve spring. If you have compression, check out the carb. I once had a new carb flood over the floats right out of the box. It ran horrible. If you have gas and compression, it must be ignition. Are your plug wires really on the right cylinder? I have seen this happen a few hundred times to people. Is you timing truly set correctly? Sometimes goofballs put a mark on an engine in the wrong place and then everyone else after them tries to time it with an incorrect timing mark. It is a neat trick. Been there and done that before. That can be really frustrating. If it has spark (at the right time), compression, and fuel, it should run fairly decently. However, like the guys in this room have suggested, it could be some other emission related "junk" as well. EGR's commonly freeze in the open position and every position in-between. If an EGR valve does this it can really make an engine run horribly, and if they stick open, you can almost forget about getting the dang thing started due to the fact that with a stuck EGR you have a monsterous vacuum leak. Also, the canister fuel problem I have read about above CAN happen but it is unlikely because these turkeys are controlled by a thermo switch that rarely fails. But, since you have been messing around with the vacuum lines you have probably taken the vacuum line off of the thermo switch located at the themostat housing. Not that it matters any, if the system is working right, your charcoal system won't do anything without vacuum. Like four-sixty said, the air pump does put air into the exhaust system to help the cat-converter burn off HC and CO. In fact I have put an air pump on modified engines that I built that would NEVER pass the clean air test. However, with an airpump and a cat converter, they go right through. I wish you the best of luck buddy. Let us know what it was.