The never ending P0171 code. 97 2.3l ranger.
#1
10-29-2017
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Location: Lenoir, NC
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The never ending P0171 code. 97 2.3l ranger.
Hey guys, I've had my truck for about a year. And since I've had it, it's had the exact same lean code. I have replaced the MAF 4 times already. I replaced the tps, iac, coil packs, plugs, wires, crankshaft sen, camshaft sensor, AND the computer. I've also had the car smokes a few time, with no leaks detected. I have a steady misfire with no code for it, and when I'm driving in neutral, the idle will stay at 2000-3000 rpm until I make a complete stop. I've also replaced the fuel rail, fuel injectors, fuel regulator, and fuel pump. I seriously do not know what else it could be at this point? Is my truck out of time? Any insight would be helpful right now. I bought better plugs, wires, thermostat, timing belt, and tensioner this weekend and I'm installing all of them Tuesday. If anyone has any ideas, I'm all ears.
Thanks
Thanks
#2
10-29-2017
Welcome to the forum
P0171 - Lean on Bank 1
On a 4cyl that means whole engine because there is only 1 O2 sensor that can cause that code to be set.
But what does it really mean?
The PCM(computer) knows it is operating a 2.3 LITER engine, so it knows how much air the engine will pull in at any RPM and throttle position.
PCM uses MAF sensor to fine tune that air flow data for temp and "weight" of the air
PCM then calculates how much gasoline it needs to add to the engine for XXX amount of air.
PCM then opens the fuel injectors which have 30psi of fuel pressure(1997) for say 100ms(milliseconds) to add that amount of fuel
PCM then looks to upstream O2 sensor data(B1S1) to see if it's calculation was correct.
If O2 sensor shows too much Oxygen(O2s see Oxygen not fuel) then it was a Lean burn.
So PCM will add more fuel, opens injectors for 102ms
Then looks at O2, if still too much Oxygen then it open injectors for 104ms, letting in even more fuel.
It does this instantly and does it until O2 reports balanced Oxygen levels
If open time for injectors is more than 20% higher than calculated then PCM sets Lean code, to let driver know there is a problem with the calculations.
20% lower and PCM would set Rich code
Your freeze frame shows normal operation, STFT is at 1-2%, so won't set Lean code, above 15% for any length of time will
So Lean/Rich codes are directly related to fuel injector open time and O2 sensor oxygen levels.
What if fuel pressure was low, say 15psi instead of 30psi?
Less fuel flows out at 100ms open time so calculations are off
What if there is a vacuum leak?
More air than reported so calculations are off
What if there is an exhaust manifold leak?
extra air is sucked in so O2 sees false Lean
What if O2 sensor is not reading Oxygen levels as it should?
What if computers calculations are in error?
What if there is a mis-fire?
OK, you have that, a mis-fire means NO OXYGEN was burned up because cylinder never fired, so all the oxygen is dumped into exhaust and O2 sees too much oxygen, Lean.
So I would cure the mis-fire first, focus on that
P0171 - Lean on Bank 1
On a 4cyl that means whole engine because there is only 1 O2 sensor that can cause that code to be set.
But what does it really mean?
The PCM(computer) knows it is operating a 2.3 LITER engine, so it knows how much air the engine will pull in at any RPM and throttle position.
PCM uses MAF sensor to fine tune that air flow data for temp and "weight" of the air
PCM then calculates how much gasoline it needs to add to the engine for XXX amount of air.
PCM then opens the fuel injectors which have 30psi of fuel pressure(1997) for say 100ms(milliseconds) to add that amount of fuel
PCM then looks to upstream O2 sensor data(B1S1) to see if it's calculation was correct.
If O2 sensor shows too much Oxygen(O2s see Oxygen not fuel) then it was a Lean burn.
So PCM will add more fuel, opens injectors for 102ms
Then looks at O2, if still too much Oxygen then it open injectors for 104ms, letting in even more fuel.
It does this instantly and does it until O2 reports balanced Oxygen levels
If open time for injectors is more than 20% higher than calculated then PCM sets Lean code, to let driver know there is a problem with the calculations.
20% lower and PCM would set Rich code
Your freeze frame shows normal operation, STFT is at 1-2%, so won't set Lean code, above 15% for any length of time will
So Lean/Rich codes are directly related to fuel injector open time and O2 sensor oxygen levels.
What if fuel pressure was low, say 15psi instead of 30psi?
Less fuel flows out at 100ms open time so calculations are off
What if there is a vacuum leak?
More air than reported so calculations are off
What if there is an exhaust manifold leak?
extra air is sucked in so O2 sees false Lean
What if O2 sensor is not reading Oxygen levels as it should?
What if computers calculations are in error?
What if there is a mis-fire?
OK, you have that, a mis-fire means NO OXYGEN was burned up because cylinder never fired, so all the oxygen is dumped into exhaust and O2 sees too much oxygen, Lean.
So I would cure the mis-fire first, focus on that
Last edited by RonD; 10-30-2017 at 10:05 AM.
#4
10-31-2017
Join Date: Oct 2017
Location: Lenoir, NC
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Welcome to the forum
P0171 - Lean on Bank 1
On a 4cyl that means whole engine because there is only 1 O2 sensor that can cause that code to be set.
But what does it really mean?
The PCM(computer) knows it is operating a 2.3 LITER engine, so it knows how much air the engine will pull in at any RPM and throttle position.
PCM uses MAF sensor to fine tune that air flow data for temp and "weight" of the air
PCM then calculates how much gasoline it needs to add to the engine for XXX amount of air.
PCM then opens the fuel injectors which have 30psi of fuel pressure(1997) for say 100ms(milliseconds) to add that amount of fuel
PCM then looks to upstream O2 sensor data(B1S1) to see if it's calculation was correct.
If O2 sensor shows too much Oxygen(O2s see Oxygen not fuel) then it was a Lean burn.
So PCM will add more fuel, opens injectors for 102ms
Then looks at O2, if still too much Oxygen then it open injectors for 104ms, letting in even more fuel.
It does this instantly and does it until O2 reports balanced Oxygen levels
If open time for injectors is more than 20% higher than calculated then PCM sets Lean code, to let driver know there is a problem with the calculations.
20% lower and PCM would set Rich code
Your freeze frame shows normal operation, STFT is at 1-2%, so won't set Lean code, above 15% for any length of time will
So Lean/Rich codes are directly related to fuel injector open time and O2 sensor oxygen levels.
What if fuel pressure was low, say 15psi instead of 30psi?
Less fuel flows out at 100ms open time so calculations are off
What if there is a vacuum leak?
More air than reported so calculations are off
What if there is an exhaust manifold leak?
extra air is sucked in so O2 sees false Lean
What if O2 sensor is not reading Oxygen levels as it should?
What if computers calculations are in error?
What if there is a mis-fire?
OK, you have that, a mis-fire means NO OXYGEN was burned up because cylinder never fired, so all the oxygen is dumped into exhaust and O2 sees too much oxygen, Lean.
So I would cure the mis-fire first, focus on that
P0171 - Lean on Bank 1
On a 4cyl that means whole engine because there is only 1 O2 sensor that can cause that code to be set.
But what does it really mean?
The PCM(computer) knows it is operating a 2.3 LITER engine, so it knows how much air the engine will pull in at any RPM and throttle position.
PCM uses MAF sensor to fine tune that air flow data for temp and "weight" of the air
PCM then calculates how much gasoline it needs to add to the engine for XXX amount of air.
PCM then opens the fuel injectors which have 30psi of fuel pressure(1997) for say 100ms(milliseconds) to add that amount of fuel
PCM then looks to upstream O2 sensor data(B1S1) to see if it's calculation was correct.
If O2 sensor shows too much Oxygen(O2s see Oxygen not fuel) then it was a Lean burn.
So PCM will add more fuel, opens injectors for 102ms
Then looks at O2, if still too much Oxygen then it open injectors for 104ms, letting in even more fuel.
It does this instantly and does it until O2 reports balanced Oxygen levels
If open time for injectors is more than 20% higher than calculated then PCM sets Lean code, to let driver know there is a problem with the calculations.
20% lower and PCM would set Rich code
Your freeze frame shows normal operation, STFT is at 1-2%, so won't set Lean code, above 15% for any length of time will
So Lean/Rich codes are directly related to fuel injector open time and O2 sensor oxygen levels.
What if fuel pressure was low, say 15psi instead of 30psi?
Less fuel flows out at 100ms open time so calculations are off
What if there is a vacuum leak?
More air than reported so calculations are off
What if there is an exhaust manifold leak?
extra air is sucked in so O2 sees false Lean
What if O2 sensor is not reading Oxygen levels as it should?
What if computers calculations are in error?
What if there is a mis-fire?
OK, you have that, a mis-fire means NO OXYGEN was burned up because cylinder never fired, so all the oxygen is dumped into exhaust and O2 sees too much oxygen, Lean.
So I would cure the mis-fire first, focus on that
#6
11-01-2017
Join Date: Oct 2017
Location: Lenoir, NC
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I don't remember what I replaced my injectors with. I bought them from.
from AutoZone. I replaced the regulator, fuel pump, and regulator last week .....
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