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2002 toyota celica gt getting code p0171 replaced air filter…

2002 toyota celica gt getting...
2002 toyota celica gt getting code p0171 replaced air filter cleaned maf sensor checked maf sensor ny unplugging it and it seems to worl as vehicle turned off once i did that. I dont see any vacuum leak car drives ok, where should i go next.
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Answered in 12 minutes by:
6/21/2017
Chris (aka-Moose)
Chris (aka-Moose), Auto Technician
Category: Toyota
Satisfied Customers: 52,153
Experience: 16 years of experience
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Welcome, I'm Chris (aka Moose). I'm here to help 365 days a year, but not every hour of the day. I try to prevent delays as much as possible. Please understand I am not there and can only advise based on what you tell me. Let's get started.

How did you verify no vacuum leaks?

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Customer reply replied 1 year ago
Sprayed carb spray around to see if idle change ( no change)

Did you spray the valve cover, PCV, all vacuum hoses, all gaskets associated with the intake between the head and MAF?

Does your scan tool allow for seeing short term fuel trim?

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Customer reply replied 1 year ago
i did the spraying, ill try again fuel trim yes, what should i be looking for in fuel trim are you concerned about fuel pressure ?

Yes I am concerned with fuel pressure. Just trying to find out what you have done so far.

Allowable operating temp idle short term trim is +/-10. Something like a +5 through +10 would be a hard vacuum leak to find. A larger number would be easier. Most common causes are:

  • Mass Air Flow (MAF) Sensor
  • Intake Manifold Gasket(s)
  • Fuel Injector(s)
  • Air Fuel (A/F) Ratio Sensor

If the MAF sensor is faulty, the calculated load reading typically is low during a wide-open throttle acceleration. The reading should go to 85% or higher. When the MAF sensor is faulty it may also have low grams per second readings. The grams per second at idle should be about 1.8 - 2.2 and at 2500 RPM and no load, the readings should be about 7.2.

Monitor both the front air fuel ratio sensor and rear oxygen sensor signals. The front air fuel ratio sensor typically reads around 3.5 volts and when the mixture is lean, in closed throttle fuel cut it will read 5 volt. If the front air fuel ratio sensor voltage sticks at 5 volts when the fuel trims increase, the sensor may be faulty. If the rear oxygen sensor reads low voltage while the fuel trim readings climb and the front sensor is not reading high voltage, the rear sensor could be faulty.

Fuel pressure at idle should be 44-50 psi.

Please make sure to rate my answer prior to logging off, as this is how I get credit for helping you. If you have not yet received 5 star excellent service from me. Please follow up so you get everything from me that you expected from the deposit you have already paid, which I get nothing of till you rate me. Rating does not close the post nor prevent replying at a later date.

Thanks Moose

Chris (aka-Moose)
Chris (aka-Moose), Auto Technician
Category: Toyota
Satisfied Customers: 52,153
Experience: 16 years of experience
Verified
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