random misfire, runs rich, engine codes

some of you may know (or probably not haha) that i bought a 96 explorer about a month ago. it had been sitting in a garage with a bad fuel pump for a year or two. i replaced the fuel pump and filter along with a hand full of other things and have been driving it on and off trying to track down this issue. its got an occasional misfire thats getting more persistent. its not a consistent misfire like a bad plug or wire. low load seems to be okay but higher load tends to make it act up, it also occasionally bucks while at cruising speed on the highway. it seems to be running really rich and gets poor mileage as well, 10-ish mpg or maybe worse. you can occasionally smell fuel but i have not seen any external leak. ive checked the FPR at one point and didnt see any symptoms of a bad regulator but i will check again since it seems to be getting worse. i spent a while today unplugging sensors and plug wires to see if i could track anything down but i think the only thing i really did was tripped a few engine codes haha

p0125 - Insufficient Coolant Temperature For Closed Loop Fuel Control
p0122 - Throttle Position Sensor/Switch A Circuit Low Input
p0401 - Insufficient EGR Flow
p0402 - Excessive EGR Flow
p1409 - Electronic Vacuum Regulator (EVR) control circuit malfunction

the CEL was on before this so i know at least one of these was a legit code, but i wouldnt be surprised if i caused a few myself. it also runs really cool, the temp gauge barely moves, maybe gets right to the very bottom of the normal range. im not sure if maybe the thermostat is bad or if a temp sensor is bad. im inclined to believe it may be the thermostat because ive never really seen the radiator get very warm. any insight would be appreciated. i suspect the thermostat or coolant temp sensor (probably thermostat though) as well as the FPR and the MAF but i dont wanna just throw money at the thing, i want ideas and opinions first! thanks!

Sticky injectors maybe?

1/2 tank of gas and can of Seafoam, take it on the road for a good drive.

Intermittent is a PITA to track down.

My '94 4.0 ranger has always run at about 1/3 on the temp gauge.

Most sensors have only 1 wire, which means they use the threaded connection for the ground, loosening and retightening can restore an intermittent ground.
Also loose or corroded ground straps/wires can give intermittent problems.

yeah, i had thought of a stuck injector but im really hoping thats not the case. the problem is slowly becoming less intermittent and more constant the more i drive it. i did use some fuel injector cleaner in about a half a tank right after i got it back on the road, thinking there might have been a little gunk in the fuel system. i put new plugs in it at the same time, ive got about 200 miles on it since then. ill pull the plugs and see if any look bad. thanks for the input, any other ideas?

It is the "sitting for a year or two" that made me think of the injectors.
Gas turns to a sticky, then hard, varnish when left exposed to air/evaporation, and the injector ends are open to air inside the intake, and the fuel lines can dry out inside leaving a residue.

The new fuel filter takes care of whats coming out of the fuel tank, but what about the fuel line from filter to engine, if it was dry there could be residue breaking up and causing injector issues.
Maybe drain/back flush it into a clean pan and see what comes out.

I have never cleaned injectors, so not sure of the procedure on that, I think it's about $25-$40 each, to have them "cleaned/rebuilt".

The mileage thing and smell of fuel really makes me think injectors.

Not sure a bad sensor issue would get worse over time, although a vacuum leak can get worse over time, and many sensors use engine vacuum to operate properly.
EGR is a prime candidate but easy to check

Throw a thermostat in the engine then reset the codes. Drive it for 25 miles and see what codes reset. If it is an egr issue it will run like i tis totally bogged down if you try to give it throttle. T-Stat being stuck open will allow the coolant to circulate too fast keeping the engine to cold. This in turn will keep the engine in open loop and keep the thing giving it extra fuel.

pulled the thermostat today and it was definitely stuck open. not very far, but i guess thats all it takes. new thermostat in and it makes heat like it should. also replaced the plug wires. there were a couple that had some damage to the boots at the plug end, not sure if it was a problem or not. also cleaned the MAF. between all the work that i did, the misfire went away. i checked codes before i started the work and i got p0125 and p0402. cleared the codes when i did the work and drove it some more, came up with p0401. any suggestions on what would cause a p0401 and/or a p0402? drivability seems fine but i would really like to clear up this code before i try to sell it. a CEL seems to be a turn-off for potential buyers

http://www.motorcraftservice.com/vdirs/diagnostics/pdf/obdsm962.pdf
check page 26 it could very well help with your issue.