Ok i hope you can figure this out. For a long time engine ran lean and i chased codes on both banks for years. Then it flipped to p0172 bank 1 running rich. For one the fuel rail plenum studs are discontinued by ford and the torque tip studs just strip and twist off when replacing injectors and gaskets to find a vacuum leak that dont exist. Then the nuts to hold down the air intake is a disater when chasing lean codes. Any suggestions to get new studs. I cant get them at any parts store.
back to the issue. chasing the lean codes i replaced the lower and upper intake manifold gaskets and fuel rail and air intake gaskets. Twice. The fuel vapor canister etc etc all the 26 yr old parts. Fuel pump twice last year. Valve cover gaskets. Then the coil pack went out twice. New plugs and shitty plug wires. (They. Charge 45 bucks for new wires and 10 bucks a plug now. And the wires suck. 3 sets in two yrs cause they break at the elbow. Ok im just bitchen now) i thought i had found the problem with the fuel fill hose that was torn at the tank. But no just another fix in this money sucking truck. Now i learn about fuel trims and track them and graph them both banks. One day i change out 3 plugs on bank two and the trims flip from lean to rich. But only p0172 bank 1. I pulled all plugs and they were black and wet and then they are white and dry. Wtf? Ltft +12 to -25. So must be injectors on bank one. Only thing left. Gas milage dropped to 1/4 tank in less than 20 miles driving. Replaced them and the gaskets and no change. LTFT -25% on both banks now. Idles great and revs up good. On highway it misses but barely notice it until i gun it and then about 65 to 75 mph it back fires through air intake. Passenger side. I compression tested it. Fuel pressure is perfect. New gas cap and radiator cap. New MAF. Reports at .02 to .04 lbs. New IAT , etc etc. Last freeze frame p0172. MAF .02. Stft bank 1 -3.2 LTFT -25. EcT 185*f TP 19%. Spark advance 15% stft bank 2 +2.4 LTFT -25. The exhaust pings and pops when i turn off the motor after driving. Has always done that. Bad. Replaced 02 sensors amd checked exhaust for leaks upstream. Even switched them just to see if problem followed them. So i throw my hands in the air. Again. On the open highway she ran great at 16 to 17 mpg. Had power. Now she is about dead and i cant let go. Help
4.0l v6 HOV 1997 xlt 4x4 regular cab color red with shell. Xx VIN. Push rod.
Chugs at idle now. No vacuum leaks. Only thing i havent done is a smoke test.

 

Hard to read without paragraphs, lol

1997 4.0l

Fuel pressure is never "perfect", its a number, lol
1997 Ranger used 30-40psi

Check the Fuel Pressure Regulator's(FPR) vacuum hose for gasoline
FPR is below alternator on the lower intake, it has the Return fuel line and a vacuum line
If it starts to leak raw fuel is sucked into the intake, via the vacuum hose, causing rich running and -25%

Reverse the upstream O2 sensor locations, if problem switches to the other bank then bad O2 sensor, new or not

 

I read it also and you are right. A hard read. Thanks Ron.

The VAC hose no fuel. Infact water is dripping out of tail pipe this morning. Thats a good sign correct?
Runs sluggy unless i get into the pedal then it picks up.

Thing about this truck is there is no live data for fuel trim. I get all the other data live. MAF 0.01 lbs/s = 4.5g/s goes upto 0.04 driving. Spark advance 15%. TP 19. No MIL yet. Reset the memory last night for LTFT. I need to finish drive cycle to get a freeze frame when check engine comes on. Cause it will. And my goodness the power steering pump is louder than the motor. That needs replaced.

Ok um. Closed loop ETC 185*. IAT 86* LTFT = -100. STFT = 0. Dont get 02 temp .

 

Am i correct that a rich code means computer is making pulse width shorter to subtract gas from being injected. At -2% at a time until -25% and code is set. Its getting air at good temp and 02 sees the mix after burn and is ok with and adjust to unburned air.
so how is the exhaust pinging and crackle with unburned fuel.

 

Yes, that is correct
After warm up the O2 sensors can be used, they need to be heated above 600degF to start to generate voltage, that's Closed Loop
O2s generate their own voltage
0.1v is high oxygen
0.9v is low oxygen
Computer tries to keep the upstream O2s around 0.4v, so they will jump around between 0.2-0.6v
Downstream O2 should see very little Oxygen since the Cats use it up to burn off pollutants, so 0.75-0.85v is expected

Once in closed loop computer does "on the fly" injector open time calculations, this is STFT(short term fuel trims)
This calculation is 0% STFT(and it is a %, -20% means a 20% difference from the computers on the fly calculation, so a big difference)
Computer then looks for feedback from upstream O2 sensor's
If an O2 shows 0.1v then computer opens injectors longer on that bank, so +2%, +4%, +6%, ect..........until it can get O2 to 0.4v average
Or if O2 shows 0.9v then the opposite, computer closes injectors sooner than calculated, -2%, -4%, -6%, ect...........until O2 is 0.4v average
If computer gets over 20% error in either direction it will set codes for that

LTFT(long term fuel trims) is stored in computers memory, its an average of STFT over time, its there so computer doesn't have to relearn the vehicles fuel systems at each start up
There are always small air leaks, fuel pressure differences, less efficient injectors or spark plugs, so LTFT of -5% to +10% is not at all uncommon, the +10% is because small air leaks, dirty MAFs and injectors, and older fuel pumps are the most common issues, but not an issue for concern

After computer does its calculations LTFT is ADDED to that, and that's the 0% STFT the computer starts with
So -25% LTFT and then -2% STFT = -27% STFT
If you fix a problem then you might see -25% LTFT but running +10% STFT so -15% BUT the +10 STFT would start to change the -25% LTFT to -15% LTFT and even lower each time vehicle was driven and warmed up

-% LTFT are not as common as +% LTFT
Fuel pressure that is too high, 1997 35psi average, fuel pump can do 80+ psi if FPR has failed or return line is blocked
Leaking FPR
Leaking injectors
Clogged exhaust
Failing computer is not off the table, but last resort

 

Each time its warmed up and driven. I am expecting an immediate change in LTFT trim. Ok.

Track and go ahead and graph the numbers and watch LTFT change in regards to STFT as it does its thing in the now. No change towards +/- 10 to 0 is time to trouble shoot further. One step at a time.

I will start with fuel line clog. Check psi from fuel pump. Maybe pull injector and make a sleeve with cleaner can and tube and pressure up and hit injector with 5volts to see if they act right. Last but not probable is the computer program.

Oh man Ron i just remebered that on bank 2 when system flipped from lean to rich i had an injector that lts plastic cap on intake side and an old one was put in its place from bank 1 and new injector put on bank one. Since bank 2 no codes. All bank 1 problems. New doesnt mean works right. But now i have 2 new injectors on bank 1. Need to double check them for performance.

I may have created this monster unknowingly. Good grief Charlie Brown.. yeah i will het back to you soon. Thanks for your time and guidance.

 

Quick question. Long time back i had to replace the ignition switch with a generic one off the shelf. It has only two positions. Key on and start. It has an accessory position but nothing turns on. Will that mess with the truck in any way?

 

Dude. I borrowed a scanner and did a test drive and recorded live data and it manually set a start point that gave me a freeze frame fuel trim data. With two weird codes and other data. Ready

Looking better but the evap ctrl valve means something else in circuit cause thats new.

 

Fuel tank pressure sensor. Negative pressure backflows gas into intake creates rich condition and makes pcm lean out injector but uses up gas.

Hence it dont make exhaust smell like gas but the exhaust is flooded with unburned gas that makes it ping and pop when motor is turned off. also makes misfire in cylinder that get gas/ fumes not matched with amount of air.

It matches my symptoms.

Good Grief Charlie Brown.

 

MOD$10 is for emissions systems, "fail" is because you have EVAP code, but can't effect running

Unless you way overfilled your gas tank the EVAP system won't "suck in" too much gas fumes
Gas tank pressure sensor is for air pressure in the tank and should be negative pressure but the gas tank is a sealed system, so once negative pressure is maxed out very little gas fumes flow into engine
With engine idling remove the gas cap, see if engine RPM changes, if so then EVAP valve is stuck open

You left off the + and - signs for fuel trims?

Are they all + trims?

 

Bank 1 -2.3. +10.5
Bank 2 0.0. +24.3
xhecking gas cap next

Ok the rpms went up from 700 to 900. Second time no change. Then the check engine light finally came on with P1443. So i plugged in scanner and this is the freeze frame.
p1443
CL
58.4 load
ECT. 176
STFT B1. +4.7
LtFT B1 -5.5
StFT B2. +4.7
LTFT B2. +0.8
RpM. 1988
MpH. 43
Spark advance 14.5
MAF 0.01 lbs/s

Thats the trim numbers im looking for. But wait need to fix evap.

I did graph the spark advance and it was all over the place but between 12 and 17. Never at a steady state.
I am gonna take a road trip from vegas to Tucson in next couple days if this is a fix i need. My brother is diagnosed with cancer and its like every where. I just went through prostate cancer myself and had it removed. But i need to go see him.

 

Thank you for all the help Ron. Trouble shooting helped me understand a lot of things. Still have the p1443 and rpms do not change with gas cap off and at idle.
also have a ruff idle. With a p302 code. Might be valves or exhaust leak. Idk. New injector on the cylinder.
the p1443 has popped up before when fuel trims where good.