Hello everyone, this is my first post hoping to see if anybody can help me with this problems that I have with my Ford ranger

It’s a 2003 Ford ranger edge 3.0 flex fuel automatic vehicle.

I got two codes after I replaced my mass airflow sensor and the codes were P0172 and p0175. I was getting terrible mpg before I replaced this part (plus all the other symptoms that I have described below) and never got any codes and so I’m assuming after I replaced it the computer finally figure it out that I was eating too much gas and gave me these two codes.


It has a rough idle on start(sometimes), just jumping RPMs, you can hear the engine just sounds weird (vrum vrum vrum vrum) also, I do get terrible mpg, I get about 15 a gallon on the highway and that’s on the good end, and if I use flex fuel, I usually get 10 to 13

things I have replaced so far on the car
spark plugs and wires
Fuel filter
Air filter
Mass airflow sensor
Master brake cylinder
Pcv valve
(Replaced one of the vacuum line hoses that connect to the intake manifold because it was collapsed around the same time I did that airflow sensor)

any help would be appreciated. It’s almost like my vehicle stuck on flex fuel mode, and it’s injecting way too much fuel.

also, for the freeze frame, it said -25 bank, one and bank two

One last thing, all the PCV valves that I buy allow air to go both ways and I don’t know if that’s normal for Ford rangers pcv valves

 

PCV Valves are the same as most on Rangers
There is a weighted valve inside, i.e. the shake test, lol
When high vacuum is applied(idle) from intake manifold then weight is lifted and PARTIALLY closes off air flow from valve cover into the intake, shouldn't close completely
When engine is under load(driving) vacuum level drops and weight drops as well, allowing more air(blowby) to be sucked into the intake
So yes, you should be able to blow into the PCV valve from either end, but one way will have less air flow

-25 fuel trim does mean computer is seeing Low Oxygen Levels in the exhaust, so should be REDUCING the open time for the injectors

The oxygen levels in the exhaust comes from the O2 sensors, the only sensors that can do this so no "backup" for these

After engine is warmed up O2 sensors can come online, so after 5min or so
Computer knows its running a 3 liter engine, so it knows exactly how much air is coming in at any RPM and throttle position, its just math
Gasoline has air/fuel ratio of 14.7/1, this is a weight ratio NOT volume
14.7 pounds of air to
1 pound of gasoline
(MAF sensor WEIGHS the air, computer already knows how much air is flowing in)

Computer also knows the fuel pressure(expected is 50-60psi, no sensor for this) and size of each injector, so 60psi thru 21lb/hr injector open for 100ms = XX weight of gasoline

Computer does this calculation on the fly, and that calculation is 0 STFT(short term fuel trim), it then checks upstream O2 sensors to see oxygen levels in the exhaust is high(lean) or low(rich)
It then adjusts its calculations using STFT
So +5% STFT means computer is opening injectors 5% longer because O2 showed high oxygen or lean
If -5% STFT then computer is closing injectors 5% soon than it calculated because O2 showed low oxygen or rich, in exhaust

LTFT(long tern fuel trims) are an average of STFT that the computer saves in memory, so it doesn't have to re-learn this one engines minor issues at each start up
LTFT is used to calculate 0 STFT
So if LTFT was -10% and STFT is -5% then actual fuel trim is -15%

O2 sensors only "see"/react with Oxygen
O2 sensors generate their own voltage, 0.1 to 0.9volts so low voltage
O2 sensor use a chemical reaction to generate this voltage after they are heated above 600degF
O2s run out of the chemicals after 12 years or 100k miles
They are the ONLY sensors that "wear out" after a certain time or miles

If you don't know the age or miles on O2 sensors then change them, so you you can start the clock on the new O2s but also so you can diagnose lean/rich issues knowing its not a FALSE lean or rich from old O2s

2001 and up 3.0l Ranger flex fuel computers have a wider air/fuel range that allows them to run up to E85 without setting codes, there is no Fuel Type sensor anymore, like what was used on earlier Flex Fuel engines
So there is no E85(flex fuel) mode or gas only mode, the computer just "looks" at the upstream O2 sensors to see if it needs to add more or less fuel

Codes are set when fuel trims get above or below +20% or -20%

If you have a vacuum gauge check vacuum level at idle 18-21" is expected
Then REV the engine and hold it at say 2,500rpm and watch vacuum, should drop and then come back up, after coming back up if its slowing dropping you have partially blocked exhaust system

 

My ranger has 152k miles on it, so I’ll change the downstream 02 sensors, also do you know any brands that I should pick

(A-Premium or bosch)

because I see a a lot of different ones? Also for checking the vacuum level can I just disconnect a vacuum line let’s say that’s on the manifold and connect the gauge on that, Or is there a certain area that I would have to test?

If The vacuum pressure is not were you said it should be would it make my engine have a rough idle? Or would that also be a part of the O2 sensors not give me the correct reading?

thank you for the help

 

Bosch is what Ford used as OEM

Usually there are unused vacuum ports with a Cap on them on the intake manifold
If not I would use a "T" to tap into any of the smaller vacuum hoses at the intake manifold

O2 sensor is not used at idle or at WOT(wide open throttle)

Misfires at idle will show up on vacuum gauge as bouncing needle, but if misfires are caused by vacuum leaks then you would also see lower vacuum levels, under 18"

 

so I change those O2 sensors to

OEM ones and the downstream one does not look like the same that I took off. It actually looks like an upstream sensor but with the same thickness as a downstream so I did contact the company to get a replaced because the part is totally different from the part that they show online. I did put it on just to see because he said just to test it and I got a P1151 and a P1131 code do you think that downstream sensor not being correct is the cause?

 

Upstream and downstream O2s are exactly the same, no difference in how they work

 

Always good to post the code numbers with definitions, no one has them memorized, lol
P1131 Lack of Upstream Heated Oxygen Sensor Switch – Sensor Indicates Lean – Bank No. 1
P1151 Lack of Upstream Heated Oxygen Sensor Switch – Sensor Indicates Lean – Bank No. 2

No, nothing to do with downstream O2 sensor, it would set one of these codes:
P1137 Lack of Downstream Heated Oxygen Sensor Switch – Sensor Indicates Lean – Bank No. 1
P1138 Lack of Downstream Heated Oxygen Sensor Switch – Sensor Indicates Rich – Bank No. 1

So your computer's air/fuel mix calculations are coming up Lean when burned in the engine
Unreported air is coming in, often a vacuum leak
But can also be low fuel pressure, expected is 60psi, would need to be under 35psi to set lean codes
Can even be partially blocked exhaust

And it may be a computer issue, no way to test that, basically eliminate everything else then replace computer
Check spark plug tips
If MPG is poor and spark plug tips are getting darker brown then you have a FALSE lean, which was either Old O2s or exhaust manifold leaks on BOTH sides, or failing computer

 

I found a exhaust leak past the cat at a seal It doesn’t leak any air but just drops of water. Would that be anything? My mpg has been better since I changed the 02 sensor… my bank 1-2 were always at -25 but now they are at +8

 

-25% would be Rich codes not Lean codes, so that is very very odd

+8% is good, that should change LTFT(long term fuel trims) the more you drive
-10 to +10 is normal STFT when cruising along, -5 to +5 when it was new, lol

 

sorry, I meant to say it was -25% before I change the 02 sensors but now that I did it is at 8