I need help, a week ago my truck popped a code and it was misfiring, 4th cylinder. I have replaced the spark plugs, wires, coil pack, and now the fuel injectors, its running lean now, the misfiring was gone but came back, i dont know what to do or where to go off from here, someone said it could be a cracked cylinder head but im not sure.

 

Unplug the mass air flow sensor and see if that makes it run better? If its dirty or broken unplugging it will make the engine run at the default settings, which is fine you just won't get as much power so you would want to replace or clean it eventually.

 

I did that and I didn’t notice a difference, I also cleaned it and still ran the same after unplugging it.

 

What fuel pressure do you have?
Expected is 55-60psi, at idle, then raise RPMs to 2,500 and hold there, watch if pressure starts to fade, go down, if so replace fuel filter first and retest, if still fading replace fuel pump

Rangers have no fuel pressure sensors, so all computer can do is set Lean codes when pressure is low

 

How do I check the fuel pressure? Would it show me in an obd reader or do I need something for it.

 

No, on the OBD, there is no fuel pressure sensor

You can rent a fuel pressure gauge, some autoparts stores rent them or loan them(free), but they only cost $25-$30 so not a big expense

There is a fuel pressure test port on the engines fuel rail(the pipes on injectors), it looks like a tire's air valve, because it is, its a schrader valve, should have a screw on cap like a tire's valve has, remove this cap, no fuel will come out, same as tire's air valve
You screw on the gauge same as you would on a tires valve, the gauge will press the center pin down as you screw it on

 

It has 65 psi consistent, what else can I check

 

Only think left is exhaust, partial blockage will cause Lean codes and then stalling when too much back pressure builds up

You would also lose power at highway speeds, so if thats not happening then not an exhaust issue

Engine/exhaust cold, tap on cats and muffler with a stick, wood, see of any rattle, breaking apart inside

You can use a vacuum gauge to test for exhaust blockage, tests to do seen here: https://www.gregsengine.com/using-a-vacuum-gauge.html

 

I have 3 codes, p0113, p0171, and p0174.

 

Quick update, got rid of the cats and it’s a little better the first code went away but it’s still lean.

 

Big vacuum leak somewhere? Spray some carbie cleaner around. Possible bad o2 sensor. You seem to have covered all the rest.