Question about 2002 Ford Mustang

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Car Running lean o2 sensor is fine.

Just like the title says. My car is running lean in the first bank and it's not the o2 sensor. Please Help!!!!!!!

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  • dylanksimmon Jun 03, 2009

    when you push the clutch in when coming to a stop it idles at 900 rpm to a 1000 then when you actually come to a complete stop being in nuetral the motor will bog down to 4 to 500 rpms. then sometimes it dies or idles fine. when driving it runs fine.

  • dylanksimmon Jun 03, 2009

    but only one side is running lean. bank one. every mechanic i have talked to has said it's not the sensor or the whole car would run lean.

  • Mike Butler
    Mike Butler May 11, 2010

    Hows it running?



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Most likely your MAF sensor is dirty. It is a very delicate wire that reads airflow in your intake and tells the fuel distribution system how much time to open the injectors. Here's a link to some Ford ones so you know what you are looking for.

They can be cleaned, here's a general how too. If you google MAF Sensor clean you'll find videos and lots of helpful hints! Just make sure you remove the sensor from the vehicle and allow it to fully dry before replacing it.
Mass airflow sensors constantly measure the amount of air entering the intake manifold. This lets the engine management computer know how much gasoline to inject into the cylinders for proper combustion. Hot-wire-type sensors, like you have, work by keeping a short piece of wire or film at a constant, elevated temperature. An electrical current is applied to the wire to maintain its temperature; the amount of current necessary to maintain the temperature is proportional to the mass of cool air flowing past it. Sounds complicated, but there are no moving parts and the response rate is very fast. So far, so good.
Eventually, dirt and oily film bake onto the wire, insulating it from the cooler air--and when the engine management computer sees a value for air mass that's too far out of range, it sets an error code. Periodically, there's a cleaning cycle during which the wire is heated to a very high temperature right after engine shutdown. This burns off deposits.
When this cleaning cycle fails to remove all of the contaminants, you're supposed to replace the MAF sensor. According to almost every manufacturer, it's not recommended or even possible to clean the delicate wires. Of course, they're selling those sensors, so their motivation might be suspect. Next time, I'd try cleaning it first--what do you have to lose? I used to use aerosol carb cleaner, but CRC MAF Sensor Cleaner is new and less prone to dissolving other components in the MAF sensor. Do yourself a favor and remove the MAF sensor from the vehicle before attempting to clean it. Also, I'd make sure the air filter housing, air filter and all associated ducting are intact, clean inside and not leaking dirt. This will keep you from needing to clean or replace the MAF sensor anytime soon.

Posted on Jun 03, 2009

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  • rjbeg123 Jun 03, 2009

    I'd have helped you if you'd just asked a question or clarified but when you give me a rating like that you're usually on your own. I actually have a very good idea of what the issue is after reading your response. Here is the list of possiblities right out of Fords tech manual....What does that mean?

    An oxygen sensor in bank 1 detected a lean condition (too much oxygen in the exhaust). (On V6/V8/V10 engines, Bank 1 is the side of the engine that has cylinder #1).

    Note: This DTC is very similar to P0174, and in fact your vehicle may show both codes at the same time.


    You will more than likely not notice any drivability problems, although there may be symptoms such as a lack of power, detonation (spark knock), and/or a hesitation/surge on acceleration.

    Causes From the book again!!

    A code P0171 may mean that one or more of the following has happened:

    • The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters (K&N, etc.) can cause the MAF to become dirty if the filter is over-oiled
    • There could be a vacuum leak downstream of the MAF sensor.

    Oh shock and horror! Look it listed the MAF sensor! I've been working on cars for over 35 years and I know what I'm talking about! Clean the MAF check for leaks, check all of the little rubber hoses that they are patent (not leaking) and connected......follow these steps and don't trash people in your ratings if you really want help...

    Possible Solutions

    Possible solutions include:

    • In the vast majority of cases, simply cleaning the MAF sensor does the trick. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with MAF cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling
    • Inspect all vacuum and PCV hoses, replace if necessary
    • Check for a dirty fuel filter and proper fuel pressure

  • rjbeg123 Jun 03, 2009

    Here is the rest of the list of posibilities from the Ford Manual:

    Air Measurement System

    • MAF sensor (contaminated, damaged, malfunctioning, etc.)

    Fuel System

    • Fuel pressure regulator (leaking, malfunctioning, etc.).

    • Fuel filter plugged, dirty.

    • Fuel pump (weak, check valve leaking, etc.).

    • Leaking/contaminated fuel injectors.

    • Low fuel pressure or running out of fuel.

    • EVAP canister purge valve leaking (when canister is "clean").

    • Fuel supply line restricted.

    • Fuel rail pressure sensor (incorrect reading).

    Air Induction System

    • Air leaks after the MAF.

    • Vacuum Leaks.

    • PCV system (leak, valve stuck open, etc.)

    • Improperly seated engine oil dipstick.

    Exhaust System

    • Exhaust leaks before or near the HO2Ss (exhaust manifold gasket, mating gaskets, etc.).

    EGR System

    • EGR valve tube/gasket leak

    • EVR solenoid vacuum

  • rjbeg123 Jun 03, 2009

    Not sure what 'mechanics you've talked to. The technitions and engineers at Ford motor company sure seem to think that the MAF may very well be your do I. They can be cleaned, there are products available specifically for cleaning the MAF sensor. Try it.



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