Got an 06 xlt with a 2.3 that threw a rod. Swapped in a 2.5 from a 12escape with vct delet and balancer delete. Keep getting too rich codes and fuel trims are way negative. Replaced oxygen sensor(heater was bad), put new 2.3 injectors in, check balancer timing set to correct. Mass air flow sensor is clean. No other codes set. Run out of ideas, if anyone could help

Etc is reading correctly

Fuel pressure?

Fuel Pump is capable of 80+ PSI, Fuel Pressure Regulator(FPR) in the gas tank should limit that to 55-60psi

But would have nothing to do with head swap, would be an unrelated issue
There is a 3rd fuel line added to the Fuel filter in 2001 Rangers, that's for the FPR in the gas tank


Rangers never had a Fuel Pressure sensor
1998 and up Ranger computers are programmed to expect 60psi
And they are programmed for injector size, say 16 pounds per hour(no idea what 2.3l should be)
Computer then "knows" how much gasoline will flow out of each injector if its open for say 100ms(milliseconds), just Math

Computer is also programmed for engine size, it "knows" 2.3 liters of air will be pulled in every 2 RPMs at WOT(wide open throttle), rest is just Math, i.e. it "knows" how much air will come in at 500rpm, 1,000rpm, 3,000rpm, ect.......

MAF sensor and air temp sensor tells computer how much that 2.3 liters of air WEIGHS
Gasoline air fuel ratio of 14.7:1 is a WEIGHT ratio
14.7 pounds of air to 1 pound of gasoline
14.7 grams of air to 1 gram of gasoline
Weight ratio

Which is why fuel injectors are rated in Pound Per Hour of fuel flow

So fuel trim of 0 is what computer calculated at this moment for the Open Time of each injector, lets say that Open Time is 100ms just because its easier
O2 sensor is the only Feedback Computer has on if this Fuel Trim of 0 is OK
If its not, which it never is, lol, it which adjust the Open Time
102ms would be +2% fuel trim
98ms would be -2% fuel trim
90ms would be -10% fuel trim, translates as Rich, even though is is technically not Lean or Rich running
If smoke is coming out the tail pipe its running Rich
If engine is pinging and knocking its running Lean

The lean and rich codes are strictly injector Open Time codes, fuel trim codes
Engine may be running perfect at -25% fuel trim, the code is to tell driver that there is a problem in the system because fuel trims should be -10 to +10 in normal operation

It could be from over reported air weight, or high fuel pressure
Leaking injector
Even Faulty computer

Checked fuel pressure the other night when it had the 2.5 injectors in it. It was quickly fluctuating between 60 and 65ish.

That shouldn't cause any issues at all

Key on engine off
Press gas to the floor and hold it down all the way
Turn key to START
Engine should just crank but NOT start
If it fires/starts then you could have leaking injector

All engine computers have whats called "Clear Flooded Engine" mode
Key on
Engine at 0 RPMs
TPS(throttle sensor) at max voltage(pedal to the floor)
This tells computer to TURN OFF fuel injectors

This allows driver to crank the engine over to DRY IT OUT if it was flooded, max air flow(throttle wide open) and no fuel being added

I use this every morning to start my high mile 4.0l OHV, I want to pump oil thru the engine before I let it start up, eliminates dry starts and annoying lifter ticks I use to get, lol
As soon as you release gas pedal, computer will start injectors, even while cranking

In any case, it can also tell you if gas is leaking in from an injector