I have a misfire on my '93 2.3L Ranger.
I don't have a check engine light.
I have replaced both coil packs, the plugs and wires. I have read that it could be O2 senors, fuel injectors or a vacuum leak.

Any idea on where to start or how to troubleshoot without a code?

 

First thing to do with a misfire is a compression test, its a pain but will save you time and money on non-fixes if there is a compression issue

1993 2.3l should show 160psi in each cylinder
For the test remove 1 spark plug from each cylinder, easiest one to get to, first
Then test each cylinder's compression and write it down

Then put about a teaspoon of oil in each cylinder and test again, write it down, this is a WET test
I use a straw dipped into a bottle of oil to add the oil

Dry test tells you if one cylinder is lower than the others, causing that cylinder to misfire

Wet test tells you if its Rings or Valves that are casing the lower compression

And no on the O2 sensor, and it would set a code

A fuel injector would be a maybe but a long shot maybe, also should set a code

Vacuum leak would also set Lean code

I would read the codes using the Check Engine Light flashing method, you can use just a plain wire as the jumper, no fuse or light is needed

Video here:

3 digit code list here: https://therangerstation.com/tech_li...gitcodes.shtml

 

@RonD Understated that I shouldn't shoot the parts canon at the problem. However, I also have read that the IAC has a history of going bad. Is there a way to troubleshoot this?

 

Yes, start the engine cold
If RPMs are high then IAC Valve is working
If RPMs slowly drop as engine warms up then IAC Valve is working

After engine is fully warmed up and idling unplug the 2 wire connector on IAC Valve
RPMs should drop to about 500 or engine may even stall, either is good it means IAC Valve is working and no vacuum leaks


My original 1994 IAC Valve is still working fine, 3rd party IAC Valves were the ones that had problems

 

@RonD Thanks for the info. I will check that, but I put the wrong acronym down. I meant to say ICM. Any tips on troubleshooting that?

 

Yes, most auto parts stores have a tester for the 2.3l ICM(ignition control module)
And yes they do have a history of failing after 20 or so years
But wiring at the ICM can also be the issue it the get old and brittle, also the Ground for the ICM was a known issue, one of the screws that holds it to the intake is the main ground, can't remember which one

 

We stopped doing a compression test like that years ago when PFI (port fuel injection) came about. We found a running compression test would show a clear picture of whats happening inside the combustion camber. The reading you will be looking for are 155 per cylinder running. Anything lower or high you have a issue. Because now you have to consider not just valves and piston and rings plus cylinder bore. The injectors come into play, and if the engine is a multi-valve. This test can help with that. Remember to remove the schrader valve from your tester.
I used it when test a V10 at the track, and needed to know something quick. I've done it on pit lane before, at Road Atl.

 

Yes, if you have the software its a quick way to test relative compression, but software or handheld device was not cheap, so for DIY who might need it one time its not really an option, shops and racers would have multiple uses so affordable

Manual test just needs the pressure gauge($25-$40) and a little time

 

I guess you have never done a running compression test and have not seen one performed. All that is need is a regular compression tester like the ones Snap-on, Mac,Matco, Sears who ever sells.
Remove the schrader valve(same as tire valve core) Attach the gauge as you normally would and start the vehicle. It takes two people, one to operate the vehicle to start it and keep it running at a low idle speed without stalling. It may take a couple of trys. No scan tool needed, no special tools or diagnostic equiptment needed. You have to put the old way of doing things away for a while. And do like this which really doesn't make sense, but it works. Your outside the box on this one, I remember balking at the idea of a running compression test. Two engineer's from Diamond Star Motors which is Chrysler Corp, Mitsubishi Motors Corp.Showed me how it was done, it was a little tough with the language barrier . We figured it out, and I learned a bunch of new stuff that day.

Ken

 

Done that many times ages ago but never did think it gave me more information that a static test.
Give me a vacuum gauge and a running engine any day, lol.

If you are pulling spark plugs to insert a gauge then static test is fine, no need to run the engine, IMO

To me a "running compression test" now-a-days is using a laptop with OBD software, like this