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Can not beat P0171


CTG3
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Hello and Thanks for the help.

 

I have been loosing a battle to P0171 for a few months now. I have checked for Evap leaks, Replaced the Maf, Pulled batterry to reset computer, Reset via scan guage, Cleaned throttle body, replaced fuel filter, new plugs and wires, and I think that is it. My pathfinder is a 2003 SE 4X4 with 140K miles on it. I am unsure what to do next. The code of course is bank 1 Running Lean. My last possibility (to me) would be exhaust? It is a northern car so the exhaust is rusty and perhaps even has a few small holes but it has newer cats. (unusure on cat details) I want to drive this for a while , really love the thing so thinking about a new bank 1 cat and 02 sensors and new cat back exhaust, could that be it?

 

Has 1 inch OME lift if that is relevent.

 

Any advise?

 

Thanks

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I hear your pain. just spent the last week or so chasing a cylinder 5 miss fire code. through careful diagnosis and process of elimination I figured it out to be a bad injector.

 

Have you checked for any Vacuum leaks? a can of carb clean works well for this. I'd even run a bottle of injector cleaner (I know it's snake oil but what do you have to loose?) through the system.

 

are you running premium gas? it does make a difference as older cars were not designed to run ethanol.

hope this helps

 

read this....repairpal.com/obd-ii-code-p0171

Edited by bushnut
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Hello and Thanks for the help.

 

I have been loosing a battle to P0171 for a few months now. I have checked for Evap leaks, Replaced the Maf, Pulled batterry to reset computer, Reset via scan guage, Cleaned throttle body, replaced fuel filter, new plugs and wires, and I think that is it. My pathfinder is a 2003 SE 4X4 with 140K miles on it. I am unsure what to do next. The code of course is bank 1 Running Lean. My last possibility (to me) would be exhaust? It is a northern car so the exhaust is rusty and perhaps even has a few small holes but it has newer cats. (unusure on cat details) I want to drive this for a while , really love the thing so thinking about a new bank 1 cat and 02 sensors and new cat back exhaust, could that be it?

 

Has 1 inch OME lift if that is relevent.

 

Any advise?

 

Thanks

 

 

So with every thing you have done the code is still there, so on bank 1 which is passenger side i think :scratchhead: one of a few things can be going on, the computer thinks you are running lean because the upstram o2 is reporting too much oxygen to the computer. This can be a faulty sensor, an air leak in you exhaust between the engine and the o2 or exhaust gas hitting the atmosphere side of your o2, extra air getting in after the maf, not enough fuel getting to one or more cyl's, or a miss on one or more cyl's. Any reason that your o2 sensor sees oxygen it reports lean even if the cyl is getting enough fuel.

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What does it mean to "blowout the vacuum lines and charcoal filter" and only the upstream 02 sensor could toss this code? The leak in the exhaust is where the cat and exhaust piping meet. and I replaced with a new Hitachi MAF OEM manufacturer for it.

Edited by CTG3
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Hello and Thanks for the help.

 

I have been loosing a battle to P0171 for a few months now. I have checked for Evap leaks, Replaced the Maf, Pulled batterry to reset computer, Reset via scan guage, Cleaned throttle body, replaced fuel filter, new plugs and wires, and I think that is it. My pathfinder is a 2003 SE 4X4 with 140K miles on it. I am unsure what to do next. The code of course is bank 1 Running Lean. My last possibility (to me) would be exhaust? It is a northern car so the exhaust is rusty and perhaps even has a few small holes but it has newer cats. (unusure on cat details) I want to drive this for a while , really love the thing so thinking about a new bank 1 cat and 02 sensors and new cat back exhaust, could that be it?

 

Has 1 inch OME lift if that is relevent.

 

Any advise?

 

Thanks

 

If I were you, the first thing I would buy is a diagnostic tool... or else you might just play the replace part game until you run out of money....

 

What I mean is that you need to know what is going on with your air/fuel ratio. For this you will need to know the amount of air coming in (MAF reading ), then the fuel pressure (to rule out a defective fuel pump), then you need to know what the computer is trying to do to fix the lean condition (this will show as your short and long term fuel trim data).. As the same time you can check if any misfire are in the package and start from there...

 

Right now you're going blind at it and it can only get worse... just my 2 cents...

 

S.

Edited by fleurys
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I have a scan gauge that can read fuel trim short term and long term will check tonight. Also ordered two new (up and down) 02 sensors for bank one today. Going to check more about the exaust leak tonight and figure where it is.

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Yes only the upstream o2 can throw that code, Is that the only code you have? Since you already have o2's ordered. replace the upstream and clear codes and see if anything comes back. If it does we need to track down either a low performing cyl, injector, or air getting in after the maf. I would bet its just a bad o2

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Well who TF knows why but my SES turned off today... We will see what happends over the next few days... The only thing I have changed , I usally pump 87 octant ethenol Free gas... LAst fill up I did 93 octane ethenoal gas..... Possibly it?

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Bad or dirty gas can cause all kinds of misery. Bad (old) or gas from the bottom of the tank (at the gas station) is a mechanics nightmare. some times it has water in it or has started to break down chemically. just as a test try filling up with premium from a busy station in a well to do neighbourhood...(Canadian spelling). the reason being is that "nice" 'hoods have nicer cars that require premium fuel. meaning that it gets replaced more often, equals "fresher" gas. As a side note my truck runs noticeably better on premium gas, and has better fuel economy especially in the cold. I figure that it is because the engine (vg33) was not designed to run on ethanol. Ethanol can cause all kinds of problems in older cars as it breaks down and eats rubber hoses and absorbs water from the atmosphere. Though your VQ engine should be immune. as it is a newer platform, I'd still try a test.

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  • 4 weeks later...

New 02 sensors and it is fixed... or in Pathfinder terms onto the next code.

 

Thanks all for the help...

 

P.S. Bank 1 Up Stream 02 sensors are properly inconvenient to get to.

 

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