A single-cylinder misfire is *almost always* gonna be ignition... plug, or coil, or on an older vehicle (like a 4cyl Dakota) distributor or wire.
Before spending money, you can move stuff around...switch the plug with #4 and see if the problem follows, then move the coil. If it's a distributor, just replace the plug wires and cap & rotor. It's cheap, it's old at this point, and it probably needs it anyway.
It could also be something like a clogged injector, or problem with valves in that cylinder, so trying to narrow it down between ignition or mixture is the cheap/easy first step.
Be happy it's a city truck and not a county truck. Those asshats in the county don't take care of their vehicles *at all*.
[This message has been edited by thesameguy (edited 02-15-2021).]