So I just got another ranger I've had it for a few months it runs and drives good but the engine is rich. I've done a whole ordeal of diagnostics to it checkin for leaky injectors and what not but can not figured it out I've had 3.0s in all my rangers (except my 80s ones) and love them and never had this issue and was hoping someone else has and figured it out side not the engine light isn't on and it does have a flat spot once in awhile. I'm leaning toward a pcm but am looking for other opinions

 

Welcome to the forum

Did you do the Clear Flooded engine test?

After engine is warmed up, shut it off
Turn key back on
Press gas pedal down to the floor and hold it down all the way
Try to start engine

It should NOT start or even fire, injectors are shut off

Release gas pedal and computer will start injectors

Have you checked the spark plug tips?
They should be a darker color if engine is actually running Rich, if not and MPG is down then you could have a small fuel line leak
In winter months gasoline has more Ethanol added to prevent water in the fuel system from freezing, so "winter fuel" will result on lower MPG


How many miles on the engine?
Or more specifically the upstream O2 sensors?
O2 sensors use a chemical reaction to read Oxygen levels in the exhaust, after 100k miles they start to run out of chemicals so will give computer a False Lean signal, which causes Rich running.

Engine temp, does the temp gauge show just below 1/2 after warm up?
Running engine colder causes Rich running

 

I haven't tried the flood test I'll give it a try it gets horrible mileage for what it it is the plugs are very dark and it has 204000 but the o2 sensor look newer but if the o2s were failing wouldn't that trigger the check engine light?

 

No, on the O2s, when they start to run out of chemicals, the computer only has the O2 sensors to see if engine is running Lean or Rich, it has nothing to compare them too except each other
When an O2 fails enough yes, there would be a code

It has an adaptive air/fuel mix call Long Term Fuel Trim(LTFT) this can allow rich running without setting codes as O2 wear out

But if they are newer then that's not the problem, but it IS troubling that no codes are being set by O2 sensors for a Rich burn, especially if spark plug tips are getting black

 

Yes this is why im leaning toward a failing computer maybe but I can't scan it my scan tool **** the bed on me and I haven't replaced it yet

 

If you have a smart phone you can get Bluetooth OBD2 reader, it uses your phone as the display, under $30, get extension cable with it, $5-$8

APPs are Free or $5

These are also good to watch live data, you see what the computer sees while driving