Idle Misfire

I have the same problem on my 89, I've heard it called a lean misfire. Try spraying starting fluid around the vacum lines, fuel injectors, egr, pretty much everywhere. Also, clean the AIC, and check the throttle posistion sensor. Do a search for threads with it, theres a ton. I've done all this and still havent figured it out. I may just bring it somewhere now.
 
Yes definatly, check it or have it checked.

Also, when was the last time you did a tune up? Like plugs, wires, cap and rotor (if you got them), PCV valve, fuel filter, air filter. Thats all i can think of, but if you havent done any of those, do them. And dont sink your money into those bosch plugs, just get the motorcraft ones.
 
I have recently put in plugs, fuel filter and air filter. Soon enough I am going to put on new 9mm Ford Racing Wires and a new cap & rotor. Right now the plugs I have in are Champion ones, so I will put in some motorcraft ones as well. Can you buy motorcraft plugs from your local Ford dealer? Because I dont know of any places around my little town where you can buy motorcraft parts. Also, everytime my car misfires at idle it makes a loud knock in the exhaust. I am also going to put in a new 02 sensor and see if all these parts make a difference.
 
I forgot to mention the O2 sensor, if you havent replaced it, do it. With the timing, have you ever replaced the belt? If not, I'd suggest it, it will go out at the worst time. I've also heard that the CHampion plugs are the same as the motorcraft ones. But if you still want to switch them, which I reccomend, you can pick them up at any ford dealer. Also, if it were me, I wouldnt spend the extra money on the 9mm wires. If you dont have any ignition upgrades, ie MSD components, then it really is unessecary. I used 8mm wires on my stock system, and I actually noticed a decrease in performance. Id say go get yourself a set of motorcraft wires. BIG difference. Good luck! Let me know if you got any other Q's.