I just purchased a 1996 Ranger with the 3.0 L v6. The truck has 104,000 miles on it, but it has only had 5,000 miles put on it since 2005 (previous owner was 94 years old and barely drove it).
The truck was idling low (500 rpm) and rough only with cold starts, and it was worse the colder the temperature was outside. The local auto parts store scanned it and came back with a code for camshaft position sensor. I replaced the sensor, oil, oil filter and air filter, and it does crank better, but I could still feel a misfire. I went ahead and changed all plugs and wires (wires were original), and I noticed that cylinder 6 plug had a lot of dry carbon fouling (all other plugs looked good). After I changed everything, I was still getting a misfire. I have put 350 miles on the new plugs, and I pulled the plug from cylinder 6, and it is already getting carbon buildup and smells more like gas than other plugs.
I went ahead and checked to make sure the new plug was getting spark and it is.
I also checked the fuel injectors with a multi-meter and cylinder 6 checked the same as all other injectors (15.5 ohms I believe), and I check to make sure the injector was getting power with a test light and it was.
I have visually looked for vacuum leaks, I have not checked fuel pressure, or changed the fuel filter. I figured if there was an issue with one of these, I would be having a problem with more than one cylinder.
I have not done a compression test yet because I would have to purchase the tool, and I did not want to do that until I have ruled out other possibilities.
Overall the truck is running good, I just want to correct this issue to avoid doing any serious damage.

I'm looking for some advice on what I should check next. I am assuming the issue has something today with the truck basically sitting the last 14 years.

thanks!

try a new coil pack

Might be the #6 injector is sticking open.