Hi all,

My brother's 2002 3.0L has been running terrible (hardly surprising) so he asked me to take a look at it. It's got quite the laundry list of codes.
I've got misfires detected on all cylinders except cylinder #1. Got P0174 and P0171 system too lean bank 1 codes. P1150 and P1130 fuel trim at limit codes and finally a P1131 lean code.

He told me he got it new plugs wires 6 months ago and got a new coil about a year ago. Guess it was already running bad back then. Apparently, it got worse. It's a lot and I don't have the truck to check out more for now so I'm not quite where to start. Any advice? Thanks!

 

Welcome to the forum

Misfires CAUSE Lean codes and fuel trim codes

O2 sensors detect Oxygen in the exhaust, the "O" part, not fuel
When a cylinder misfires NO Oxygen was used, burned up with the fuel, so that Oxygen goes into the exhaust manifold and the O2 sensor reports High Oxygen(lean) to the computer
Computer adds more fuel, only thing it can do, so fuel trims go higher and higher

So you have to solve the Misfires FIRST
On the 3.0ls you need to do a compression test, they are subject to burnt exhaust valves, like all engines, but tends to be more common on 3.0l Vulcan engines
Remove all 6 spark plugs first
Then test each cylinder and WRITE DOWN results
Expected is 160psi average on 3.0l

I would also test Fuel Pressure just to take that off the table, there is a test port on the engine, looks like a tire's air valve, and works the same way, screw a pressure gauge that can go to at least 100psi to that port
Engine running you should see 50-60psi pressure in a 2002 Ranger(1998 and up)
If Lower than 40psi change fuel filter first, if still low change fuel pump assembly in the gas tank, the whole assembly