I have a 1993 Ranger, 4x2 manual transmission. It was running great until just a couple days ago the engine started to stutter while idling or at lower rpm. Google searches have everything from an engine misfire to a bad fuel injector. The engine has never cut out on me(yet, it's felt pretty close a couple times). Is there any inexpensive ways to test what could be causing this?

 

Welcome to the forum

1993 Ranger had 3 engine options, 2.3l, 3.0l and 4.0l, which do you have, it matters?

You already know you have a misfire if engine is shaking and starting to stall out.

Yes, could be time to change the spark plugs, they do wear out
Bad fuel injectors is possible but not as likely

Clean MAF sensor, need to do this every 2 years or so

After engine is fully warmed up and idling, unplug the IAC Valve
IAC Valve will close and engine RPMs should drop to 500 or engine may even stall, either is GOOD, it means no vacuum leaks, if RPMs stay high, 700+, then you have a leak

Water in the gasoline?
"bad" gas" is also an option, did you notice the problem the day after filling up?
Any water settles to the bottom of the gas tank when a vehicle sits for a few hours, and fuel pump sucks in from the bottom of the gas tank so...............higher concentration of water which can effect idle more than higher RPMs
All gas has water in it, too much is called "bad gas"
You can added Methanol(HEET, Octane Boost) to the tank to "absorb" the water

But engine size will be helpful for more info and tests

 

It is the 2.3l 4 cylinder engine with 8 plugs. It did start happening the day after filling up, about 70 miles after or so.
This morning I drove around town and it happened a couple times, but after going to class and driving again about an hour later it didn't happen at all. I have noticed it happens more after sitting for a couple hours/overnight.

 

A 4cyl engine has a high vibration factor on a misfire, only 1 cylinder fires every 180deg of crank rotation, so stumbles quite badly, especially at low RPMs
V6 or V8 engines fire every 120deg so misfires are often heard and only felt under load

Add some methanol to tank or fill up with Regular gas that has methanol added

It could be a "cold" start engine issue, after sitting a few hours, but wait another day or two to make sure it wasn't just some "bad gas"

 

Update: I dumped a bottle of octane booster and it worked great. Not sure if it was related but I also replaced the fuel filter and it's been running great sense. Thanks!

 

Good work

Thanks for the update