Not hijacking: I have posted recently after many repairs on a poorly maintained 1990 4Cyl about a stumble at about 1700-1800 rpm dependent on load (uphill grade even slight) and a pop at ignition on (exhaust backfire). I have been through EVERY system...... I believe this engine (#2 used with 100k or more on it) has 300k plus mile injectors sitting on it. My engine runs very well (NOW) but at 17-1800, its stumbles abd can throttle through it. That to me (not a guru!) says AFR is lean. Some of my injecotrs have the paint burned off as the driver side spark plugs were left loose enough to vent combustion products into them.
The only way I could ensure it was fuel (most likely) was to follow "electrical first" as a rule (all basic operational functions present to some degree already).
I had RonD's help with diagnosing a bad ICM (as well as a guide to rough testing with both standard 12v test lights and LED type high impedance). But I had more disorders. There is a guide (easycardiagnostic..... something or other), on ford DIS ICM troubleshooting. It will help you verify the crank/cam trigger, coil outputs, IDM line, power, ground, wire path resistance. I had a bad miss due to ICM failure, a bad coil driver in it, a bad coil as well, wiring faults.... The electrical you can troubleshoot relatively easy and determine a failure or fault, the injectors are going to be more difficult because unless you mitigate the electrical side (ignition, MAF, etc) operation, then all of them show similar driving symptoms to the injectors.
RonD mentioned intermittent vs consistent faults above. I had intermittent in the electrical and sensors, once those resolved, all other faults became as consistent and repeatable as the Sun rising.
Im not sure if its ok to post a link like this, if so I have done so in ignorance and will delete if instructed to.
2.3L Ford Ranger Index of Articles
easyautodiagnostics.com
This GREATLY helped me to determine the performance of the engine triggers, the power, ground and coil driver operation.
I also found a can or two of Electronic Contact Cleaner (my engine bay was infused with OIL in every nook anc cranny), a 12V penetrating test probe (Harbor Freight for like $6) and its LED counterpart from same and a DVM really made it easy to see the faults.
As well resistance checks on the coil towers pretty much pointed the finger at specific faults I could not waste time and money on.
The suggestion is to vet the ignition, ECU, COILS, crank/cam sensor and wiring first. Clean every connector sterile and ensure there are not wiring faults or frays at the connectors. Then look at fuel. That was the directive I was given a few months ago and I found success following it.
If you do end up with an ICM need, Standard Products T series from RA was the cheapest I could find and it performs as it should. Rock Auto killed everyone else for price and delivery speed by a large margin.
I also had the coil DIE due to a cracked/broken heat shiled on exhaust side. Nobody knew it had fallen out of position (maybe they did and didnt fix it). That coil failure was allowing the engine to run and run smooth at times, but when taxed it fell down. I welded the heat shield and reinstalled. It was simple crap that killed my system and assumptions of "needed repairs" by others that created such huge issues.
All to say, vet the electrical (completely) on the ignition before running down other systems (i.e., RonD directive!)