Thanks for the add from Utah just got my first Ranger pickup well I guess you can say second I have a 1977 really impressed with this 2003 Ford Ranger XLT FX4 manual transmission 4.0 just need to figure out some of the problems it has but other than that I'm loving it

 

Welcome to the forum

Common issues with the earlier Ranger 4.0l SOHC engines(2001-2004) were PVC hoses cracking at the elbows, under side of hose so out of sight.
Also thermostat housing would crack and leak.

And Timing chain tensioners, this lead to chain guides being broken and full timing chain replacement was needed, have to pull the engine to do that.
You can change 2 of the tensioners without alot of work, 3rd is behind front engine cover, timing chain cover, which requires a bit more disassembly.
If you hear an engine rattle then it may be too late, if you don't then I would put aside some time to change them, if they haven't already been changed.
Once the newer design(2005 and up) tensioners were installed there were no more issue with this.

The M5OD-R1HD manual transmission uses ATF, yes, automatic transmission fluid, it should be checked periodically, Mercon is spec'd

4.0l SOHC engine runs 9.7:1 compression ratio, so makes good power on Premium gas, but also runs just fine on Regular gas, you do lose a bit of power with Regular gas and Knock sensor advancing the spark timing, but not much.

All around the 2003 was a good year for the Ranger no real changes so no real goof ups, lol.

 

this is the issue that I am having currently misfire on cylinder 1 misfire on Startup it has brand new spark plugs brand new spark plug wires and I have changed out the coil twice also I have a bad ABS sensor