Missing on one cylender

A quick way to check the single coil pack if you know for sure which cylinder is miss firing and its setting a code you can swap the coil pack to another cylinder and see if the miss changes from one cylinder to another. If it travels to where you moved the coil then the coil is bad,if not you have other problems.

have you checked fuel injection may have faulty injector, or vacume leak. asuming you have good compression on #1 clynder

If the spark plug wires are good, replace the coil pack.

Depending on your vehicle is the coil pack good? If so with car running unplug the alternator and see if the engine smooths out, if so replace the alternator. The alternator can have a short inside causing a misfire code, if coil pack, wires, and plugs are good.

the fuel injectors can be the cause.first you must isolate which cylinder is shutting down. When the engine is missing pull plug wires one at a time to determine which one does not slow or make engine run worse. CAUTION: use rubber handle pliers or rubber glove to pull wires off plugs.

Did you have it cleared after you replaced parts? if not it may take 50 ignition cycles to clear it out. but if you feel it missing still you may have a sticky injector.

Probably one of a few easy things. Did you replace one plug at a time? If not, a couple crossed wires will be it. Recheck wires. Make sure all wires are firmly on each plug., Verify the plugs installed are the correct plugs for your truck, AGSF22FSM with a gap of .044, or others brands a gap of .054. Platinum plugs are OEM. Did you check gaps on plugs you installed? Some get dropped by employees. Don't scrimp with cheap plugs!! If you still have original wires trash them and get a quality set!

Cmashaft or crank shaft position snesors. Find their location and clean them 1st then re-try.

an engine needs fuel, air, and spark. it sounds like you have spark covered. try injector cleaner. if one brand doesn't work try another. at different times i've had luck with techron, seafoam, and lucas, which are about as different as they can be. its also possible that the problem is the injector itself or the wiring, but try cleaning it first. If the air filter or throttle body are dirty, which is rather likely on a '91, change the air filter and use use carb cleaner or seafoam. Also clean/change the PCV valve and clean the idle air control valve.

You may consider tracing back from coil back to the main plug and checking wires going into and coming out of the plug for any broke wires make sure to look for collapsed casings sometimes the wires will break internally