So two out of eight of my spark plugs are not firing. I determined this with a timing light on each of the wires. I replaced the coil packs and spark plugs/wires their gapped right. It used to run just fine with all 8 firing but not recently I lost a lot of power. Any ideas why spark plug 3 and 4 on the front coil pack isn’t firing?
2.3l 1997 Ford Ranger XLT 5 speed

 

OK, first, both spark plugs in each cylinder fire at the same time, there is no alternating, just to take that misinformation off the table, sorry just see that posted all the time

And its a Waste spark system which means cylinders fire in PAIRS, 1/4 fire at the same time at each TDC, and 2/3 fire at the same time, so one spark is "wasted" on the exhaust stroke, just easier to run a distributorless spark system this way, not for emissions, lol, another popular myth

There are 2 coils in each coil pack
so wiring will look like this
[1 4]
[2 3]
or
[4 1]
[3 2]

As long as 1 and 4 share the one coil, the order doesn't matter, same for 2 and 3, because "the pair" both get spark

So you can swap 1 and 4 around on coil pack to see if 1 stops working and 4 starts working, that would indicate a coil pack problem, if 4 still didn't work then it would be a wire or spark plug issue
Same for 2 and 3

You can also run the engine on just one coil pack, this engine ran just fine from 1974 to 1988 on 4 spark plugs
So unplug the 3 wire connector on 1 coil pack and pull it away from coil so it can't ARC
Start engine, if its smooth all 4 spark plugs on that coil pack are working, you can drive it this way
Shut engine off and reverse it, unplug other coil pack
If there are misfires you will know, engine will barely run


In 1995-2001 Ranger 4cyl the computer ungrounds the coil in the pack to fire 1/4, on both coil packs at the same time, so if just 4 doesn't work and 1 does, computer is working OK, and wiring to coil pack is working OK
So you are down to the 1/4 coil in that pack or the wire and spark plug
Swap wires around


Dual spark plugs are used for extra power, but hard to do with distributors, so when car makers moved to distributorless systems dual spark plugs made sense
BUT......4 valves per cylinder and dual over head cams get even better power, and a better use of head space, so in car engines it was short lived
With just 1 spark plug in two different cylinders not working , it would only be a slight power drop


You have a 4cyl Lima engine with a timing belt, belt needs to be changed every 80k miles or so, belt can stretch a bit as it gets older, so you lose compression and over all power