Last week I got an '04 4.0 Ranger that runs and drives mostly well and is inspected with emissions (Pennsylvania) for a whopping $750! It has a damn near perfect frame (slight surface rust) and only a few common rust holes on the bed and cab. I have a welder so that's no biggie! Yesterday I got an OBDLink mx+ scanner to try to find which cylinder is misfiring under slight load around 45ish mph. Well, today I took it for a ride with the scanner plugged in. On startup, cylinder 3 misfire. Hasn't had a problem at idle till today lol. Go down the road...running rough! Go up a hill, rough. Get to the top of the hill, smoothing out! She warmed up and calmed down. Cool. Hit a few 45mph hills to try to recreate the misfire....nope. Ugh. So I guess I'll just keep it plugged in and see what codes I get. Next weeks pay will go toward some new plugs, wires, and coilpack. I had theorized that I could fix the misfire at 45 with an altered PID with the scanner but I'm thinking that's not the right fix right now. If after the new plugs and whatnot it still has trouble chooching at 45 then I can tweak the mix at that rpm under that load in that gear.

 

Welcome to the forum

Good buy on that 2004

Plan on changing the 2 long chain tensioners on any 4.0l SOHC engine when you get it, they last 100k miles but always good to start your own clock on that, since engine needs to be pulled if there is a timing chain issue, they get whats become known as "the death rattle" on startup and mid-rpm, that means a chain guide has broken so engine must come out to repair it
Not at all hard or expensive to change these two tensioners, use only Motorcraft or Cloyes brand

Misfires are 95% of the time a valve issue, exhaust valve
When changing the spark plugs pull all 6 out first, keep them in order 1 thru 6, have a good look at the tips, they can tell you A LOT about cylinder conditions
Then test compression in each cylinder, 170+ psi is expected but depends on the gauge, what you are really looking for are cylinders that are 15% or more below your average psi
This will save you time and money when you end up chasing your tail on spark or fuel misfires and it's a valve issue

2004 is the first year of the HEC(digital dash) in Ranger
Also first year for the SJB(body computer), cab fuse box is part of the SJB

You have the 4.0l SOHC engine, used 2001 thru 2011 in Rangers, very reliable engine if timing chain tensioners are changed
The thermostat housing is plastic and has a tendency to crack or leak, you can get metal replacements now
1990-2000 Rangers used the 4.0l OHV, not the same engine of course

If automatic its a 5R55E model
If Manual is the M5OD-R1(M5R1)

2004 Ranger Owners manual found here: https://www.ranger-forums.com/genera...1-models-3747/

 

Thanks for all the great info! My dash isn't digital but I'm gonna look for one now! My Odometer says 328,000 lol. I'm probably gonna look for a motor and build it up for turbo. As long as this one is getting me to work I'm not too worried about it but I like to tinker lol. I haven't had time to pull the plugs but I might do that tomorrow if it's not raining. Dude that sold it to me was kinda hinting that they're not the iridium ones so I'm gonna try that first. I'm taking Monday off work too so I'll probably clean the whole engine bay up (it's super dirty!) and maybe pull some things apart. As far as that timing chain, I read somewhere that you can get to it from the wheel well.

 

The odometer/trip meter is digital.
2003 and older used a mechanical odometer/trip meter