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97 2.3 cylinder one running lean


3ncrypt3d

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CEL is on, and it's giving the cylinder one bank is lean, and the EVAP purge valve. From why I've seen online, this is most likely related to a vacuum leak. So, I've checked all the vacuum lines that I can see(only 2. I don't know if there's any more), one from the intake and one from the EGR valve. The one on the intake has suction, and the line was fine. The one on the EGR valve didn't have any, but I don't know if that could be an issue or not. When I checked it, the temp was where it usually sits, a little below half. My engine itself is running fine, idling steady and isn't misfiring. If anyone else has some ideas on what it could be, that would be appreciated.
 


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RonD

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Welcome to TRS :)

4cylinder engines only have 1 Bank and 1 O2 sensor that detects Lean or Rich
V6 engines have 2 Banks and 2 O2s, that is why there is Bank 1 and Bank 2 in the OBD codes

So not Cylinder #1 issue, general engine issue, Lean.

Lean code means O2 sensor is detecting too much oxygen in the exhaust.
When that happens computer adds more fuel to correct the problem but it also sets a code to notify the driver that it had to add more fuel than calculated.

So engine is not actually running Lean.

Computer uses the MAF(mass air flow) sensor to get the amount of air coming into the engine, it then uses the 14.7:1 air:fuel ratio to calculate how much gasoline it needs to add to that amount of air.
Computer opens injectors to add that amount of fuel
Then it gets feedback from the O2 sensor, an O2 sensor can only "see" oxygen
If too little Oxygen is in the exhaust then that is Rich, so computer reduces the Open time of the injectors.
If too much Oxygen then that is Lean and computer opens injectors a little longer.

So Lean or Rich codes are based on the Computer calculations
And the computers calculations are based on the sensors.

The reason a Vacuum leak is suspected with a Lean code is because not all the air coming into the engine would be passing thru the MAF sensor, so MAF sensor is under reporting the amount of air, so computer calculations would be off.
This would include ANY air leak between MAF sensor and intake valve, so not just a vacuum leak, any air leak.

Easy test for vacuum leak is to warm up the engine and let it idle
Unplug the IAC(idle air control) valve's 2 wire connector
Idle should drop to 500rpms or engine may even stall, either is good, it means no vacuum leak.
If idle stays above 700 then there is a leak

If no vacuum leak then you could have a leak in the air tube between MAF and intake.
O2 sensors wear out, recommended change time is 100,000 miles, if MPG is not what it once was change O2 sensor.
If exhaust manifold has a leak air will be sucked in, O2 sees that as Lean because of the extra air/oxygen.

MAF sensors don't usually fail but they do get dirty, they should be cleaned every 2 to 3 years, if you live in a dusty place then every year, you need a non-residue spray cleaner, electronic cleaner or they do sell MAF cleaner at parts stores


EVAP purge valve uses Vacuum.............................so, that could be the leak
 
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tomw

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Along the lines of an 'unknown' air supply noted by RonD - check that the ribbed tube that connects the MAF air to the throttle body doesn't have cracks or splits. If the engine moves,(it does) the ribs or cracks may open up and allow excess air, but close up when at idle.
tom
 

3ncrypt3d

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Welcome to TRS :)

4cylinder engines only have 1 Bank and 1 O2 sensor that detects Lean or Rich
V6 engines have 2 Banks and 2 O2s, that is why there is Bank 1 and Bank 2 in the OBD codes

So not Cylinder #1 issue, general engine issue, Lean.

Lean code means O2 sensor is detecting too much oxygen in the exhaust.
When that happens computer adds more fuel to correct the problem but it also sets a code to notify the driver that it had to add more fuel than calculated.

So engine is not actually running Lean.

Computer uses the MAF(mass air flow) sensor to get the amount of air coming into the engine, it then uses the 14.7:1 air:fuel ratio to calculate how much gasoline it needs to add to that amount of air.
Computer opens injectors to add that amount of fuel
Then it gets feedback from the O2 sensor, an O2 sensor can only "see" oxygen
If too little Oxygen is in the exhaust then that is Rich, so computer reduces the Open time of the injectors.
If too much Oxygen then that is Lean and computer opens injectors a little longer.

So Lean or Rich codes are based on the Computer calculations
And the computers calculations are based on the sensors.

The reason a Vacuum leak is suspected with a Lean code is because not all the air coming into the engine would be passing thru the MAF sensor, so MAF sensor is under reporting the amount of air, so computer calculations would be off.
This would include ANY air leak between MAF sensor and intake valve, so not just a vacuum leak, any air leak.

Easy test for vacuum leak is to warm up the engine and let it idle
Unplug the IAC(idle air control) valve's 2 wire connector
Idle should drop to 500rpms or engine may even stall, either is good, it means no vacuum leak.
If idle stays above 700 then there is a leak

If no vacuum leak then you could have a leak in the air tube between MAF and intake.
O2 sensors wear out, recommended change time is 100,000 miles, if MPG is not what it once was change O2 sensor.
If exhaust manifold has a leak air will be sucked in, O2 sees that as Lean because of the extra air/oxygen.

MAF sensors don't usually fail but they do get dirty, they should be cleaned every 2 to 3 years, if you live in a dusty place then every year, you need a non-residue spray cleaner, electronic cleaner or they do sell MAF cleaner at parts stores


EVAP purge valve uses Vacuum.............................so, that could be the leak
Thanks for the detailed response, the bank 1 and 2 is good to know. So, I did as you recommened and unplugged the IAC, and the engine died almost instantly. Which I'm assuming means there's no vacuum leaks. Which is good. I'm assuming that that means the EVAP purge should be fine? Please correct me if I'm wrong though. The bad, is the code is still there. I inspected my air intake for any cracks or holes, and I didn't see anything. On my engine, I didn't see any O2 sensors that were obvious, except for the one after the Catalytic converter. Is that the one you're talking about when you said bank one/ sensor one? My thinking is that if it's not a vacuum leak, and the intake doesn't have anything wrong with it, then it's that sensor. My exhaust is fine(albiet a little rusty...), no holes in it or anything.


Along the lines of an 'unknown' air supply noted by RonD - check that the ribbed tube that connects the MAF air to the throttle body doesn't have cracks or splits. If the engine moves,(it does) the ribs or cracks may open up and allow excess air, but close up when at idle.
tom

I checked the tube, and I didn't see anything obvious. I could replace it altogether, but I'd rather not replace something unless it's bad.



Edit: I checked the intake again, and the little hose that goes from the top of the valve cover to the intake only has one hose clamp on it. That's the only spot that I can see where air could get in in the entire intake. I don't think that's the issue, but I'm gonna get a hose clamp for it.
 
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RonD

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There will be two O2 sensors on a 1995 and up 4cyl Ranger
The one you saw, after Cat converter, is called the Downstream O2 sensor, it is there to check if exhaust is being "cleaned up" by the Cat converter, it only plays a very small part in Lean/Rich calculations by the computer.
This O2 sensor is called B1S2 in OBD code lingo, Bank 1 Sensor 2

Just after the exhaust manifold on the exhaust pipe will be the Upstream O2 sensor, this is the main O2 sensor the computer uses for Lean/Rich calculations
Called B1S1, Bank 1 Sensor 1

It is there for sure but could be out of view.

The is no physical difference between these two O2 sensors they look and work the same.
Upstream O2 sensors need to be replace more often than downstream, 100k miles is recommended change interval for upstream O2's

Thats good that you don't have a vacuum leak.
Check the air tube from MAF sensor to intake.

Hose from valve cover to intake manifold could be the PCV Valve hose, PCV Valve should be replaced every 2 or 3 oil changes.
It has a valve inside that is sucked closed by engine vacuum, if you shake a PCV valve you should hear it rattle like there is a pea inside, lol, while this means the valve is not stuck it doesn't mean valve is good, like many believe.
These are not expensive to replace.
If valve is not able to fully close it can let in more air in to the intake than computer is allowing for so could cause a lean code, long shot but not 0 shot.

Clean MAF sensor.

Lean means there is more air than fuel after computers calculation
And usually that is because MAF is dirty so under reporting the air flow, or there is an air leak, so not all air is flowing thru the MAF sensor.

But there is another side to the air/fuel equation, the fuel side.
Computer has no Fuel Pressure gauge or sensor, nor can it tell how much fuel is actually flowing into the intake when it opens the injectors.
1997 Rangers used 35psi fuel pressure systems(1998 and up used 65psi), so computer was programmed at the factory to expect 35psi at each injector, so computer knows how much fuel will flow thru the injector if it is being pushed in by 35psi.
And computer calculation is based on the 35psi, if fuel pressure was actually 20psi then less fuel would flow in, and O2 would show Lean, so computer has to open the injectors longer, and it sets the Lean code.
Not because of too much air but because of too little fuel.
 

3ncrypt3d

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There will be two O2 sensors on a 1995 and up 4cyl Ranger
The one you saw, after Cat converter, is called the Downstream O2 sensor, it is there to check if exhaust is being "cleaned up" by the Cat converter, it only plays a very small part in Lean/Rich calculations by the computer.
This O2 sensor is called B1S2 in OBD code lingo, Bank 1 Sensor 2

Just after the exhaust manifold on the exhaust pipe will be the Upstream O2 sensor, this is the main O2 sensor the computer uses for Lean/Rich calculations
Called B1S1, Bank 1 Sensor 1

It is there for sure but could be out of view.

The is no physical difference between these two O2 sensors they look and work the same.
Upstream O2 sensors need to be replace more often than downstream, 100k miles is recommended change interval for upstream O2's

Thats good that you don't have a vacuum leak.
Check the air tube from MAF sensor to intake.

Hose from valve cover to intake manifold could be the PCV Valve hose, PCV Valve should be replaced every 2 or 3 oil changes.
It has a valve inside that is sucked closed by engine vacuum, if you shake a PCV valve you should hear it rattle like there is a pea inside, lol, while this means the valve is not stuck it doesn't mean valve is good, like many believe.
These are not expensive to replace.
If valve is not able to fully close it can let in more air in to the intake than computer is allowing for so could cause a lean code, long shot but not 0 shot.

Clean MAF sensor.

Lean means there is more air than fuel after computers calculation
And usually that is because MAF is dirty so under reporting the air flow, or there is an air leak, so not all air is flowing thru the MAF sensor.

But there is another side to the air/fuel equation, the fuel side.
Computer has no Fuel Pressure gauge or sensor, nor can it tell how much fuel is actually flowing into the intake when it opens the injectors.
1997 Rangers used 35psi fuel pressure systems(1998 and up used 65psi), so computer was programmed at the factory to expect 35psi at each injector, so computer knows how much fuel will flow thru the injector if it is being pushed in by 35psi.
And computer calculation is based on the 35psi, if fuel pressure was actually 20psi then less fuel would flow in, and O2 would show Lean, so computer has to open the injectors longer, and it sets the Lean code.
Not because of too much air but because of too little fuel.
Would it be a good idea then to replace the B1S1 sensor then? I'm almost to 100k miles currently(95,700). I actually replaced my PCV valve about 2 weeks ago. The hose from what I could find helps the engine heat up faster, or something like that. As far as fuel pressure goes, I have no idea. Is there an easy way to check fuel pressure?
 

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Close enough to 100k to change it, MPG will go up a bit, as they get older the MPG starts to drop, isn't much but isn't 0 either :)
O2's use a chemical reaction just like car batterys, and just like car batterys the chemicals wear out/get used up

On the fuel rail with the injectors is a fuel pressure test port, looks like a tire's air valve because that is what it is, a schrader valve, might still have a cap on it, just like a tire's air valve, thats is where pressure gauge attaches
 

tomw

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I would try plugging the charcoal canister line feeding the intake. If the solenoid valve is stuck open, there's extra air coming in, which can cause a lean condition.
An O2 sensor will work a long time, and most get 'poisoned' by the stuff in the exhaust flow. RTV silicone, anti-freeze, coolant, gasket sealers, carb cleaners and some other (MAF) cleaners can produce 'stuff' that coats the O2 sensor or 'hooks' to the coating on one side of the sensor or the other, reducing effectiveness.
A catalytic converter OTOH, does not get 'used up' in being a catalyst. A catalyst is involved in 'getting a chemical reaction going', participatory, but not sacrificial or consumed in the reaction. It 'helps' reactions get going, some that will not take place unless the catalyst is there for the chemicals to 'touch' upon. The converters don't wear out, they get poisoned, by the same things(mostly) as the O2 sensors. They can also melt if fed unburned fuel, such as when a COP dies or a spark plug fails.
If you have OBD-II, you can watch your O2 sensors 'flip' back and forth, the quicker the 'flip' rate, the better the fuel:air ratio is controlled, closer to stoichiometric(perfect burn), and thus best economy. If the O2 sensor dies, the computer will likely add more fuel, and upon total failure, will throw a code and light the SES or CEL indicators.
tom
 

3ncrypt3d

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Close enough to 100k to change it, MPG will go up a bit, as they get older the MPG starts to drop, isn't much but isn't 0 either :)
O2's use a chemical reaction just like car batterys, and just like car batterys the chemicals wear out/get used up

On the fuel rail with the injectors is a fuel pressure test port, looks like a tire's air valve because that is what it is, a schrader valve, might still have a cap on it, just like a tire's air valve, thats is where pressure gauge attaches
I checked the PSI, so here's what I got. With the engine off, key forward, 30PSI. With the engine on, and the vacuum hose attached to the fuel pressure regulator, it was about 25. With the vacuum hose off, it was 30.


I would try plugging the charcoal canister line feeding the intake. If the solenoid valve is stuck open, there's extra air coming in, which can cause a lean condition.
An O2 sensor will work a long time, and most get 'poisoned' by the stuff in the exhaust flow. RTV silicone, anti-freeze, coolant, gasket sealers, carb cleaners and some other (MAF) cleaners can produce 'stuff' that coats the O2 sensor or 'hooks' to the coating on one side of the sensor or the other, reducing effectiveness.
A catalytic converter OTOH, does not get 'used up' in being a catalyst. A catalyst is involved in 'getting a chemical reaction going', participatory, but not sacrificial or consumed in the reaction. It 'helps' reactions get going, some that will not take place unless the catalyst is there for the chemicals to 'touch' upon. The converters don't wear out, they get poisoned, by the same things(mostly) as the O2 sensors. They can also melt if fed unburned fuel, such as when a COP dies or a spark plug fails.
If you have OBD-II, you can watch your O2 sensors 'flip' back and forth, the quicker the 'flip' rate, the better the fuel:air ratio is controlled, closer to stoichiometric(perfect burn), and thus best economy. If the O2 sensor dies, the computer will likely add more fuel, and upon total failure, will throw a code and light the SES or CEL indicators.
tom

To what charcoal canister are you referring? I do have OBD2, but I don't have a scanner. I have one I can use, or I can get it scanned at a local auto parts store. I believe the error I was getting was P1443, and P0171.
 

3ncrypt3d

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Just a follow up post, found the issue and it's been running great for almost 1k miles. I replaced the fuel pressure regulator, and I haven't had any lean codes since. The way I deducted to replace that, if anyone else is interested, is I popped off the vacuum hose, and it smelled like gas. I took it off and the diaphragm had failed.
 


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