P0171 & P0174 OBD Trouble Code

[drewlane]

1995 Lincoln Continental

Got the old "Service Engine Soon Light" a few weeks ago.

Took it to AutoZone for a code read.

Code Reader reported P0171 and P0174.

Looked up those codes on the obd-codes site and see that it says "too much oxygen in the exhaust".

Possible causes:

1. MAF sensor is dirty
2. Vacuum leak

I reset the Service engine soon light by disconnecting the battery, but the light came back on a few days ago.

Where is the MAF sensor located on this vehicle?

How do I determine if it's a vaccum leak?

Thanks,

Drew

[Towncar]

Mass Air Flow (MAF) Sensor

The mass air flow sensor (MAF sensor):

• is located between the air cleaner element (ACL element) and the air cleaner outlet tube.
• is integral to its conical housing.
• uses a hot wire sensing element to measure the amount of air entering the engine. Air passing over the hot wire causes it to cool.
• sends out an analog voltage signal to the PCM to determine the intake air mass and then calculates the required fuel injector pulse width to provide the desired air/fuel ratio.
• has a hot wire sensing element and housing which are calibrated as a unit and must be serviced as a complete assembly.

Removal and Installation
1. Disconnect battery ground cable.

2. Loosen engine air cleaner tube clamp on air cleaner outlet tube. Disconnect air cleaner outlet tube from mass air flow sensor (MAF sensor).

3. Disconnect engine control sensor wiring from mass air flow sensor.

4. CAUTION: The mass airflow sensor hot wire sensing element and housing are calibrated as a unit and must be serviced as a complete assembly. Do not damage the sensing element (internal to housing) or possible failure of the mass air flow sensor may occur.

Release mass airflow sensor to engine air cleaner retaining clamp and remove mass air flow sensor.

5. CAUTION: The mass airflow sensor hot wire sensing element and housing are calibrated as a unit and must be serviced as a complete assembly. Do not damage the sensing element (internal to housing) or possible failure of the mass air flow sensor may occur.

To install, reverse Removal procedure. Connect engine control sensor wiring to mass air flow sensor. Tighten engine air cleaner tube clamp to 3.4-5.2 N-m (30-46 lb-in).

NOTE: (warning)
There is a definite possibility of damaging the MAF or the wiring or anything else you may have to handle in performing these procedures. DO NOT TOUCH THE ELEMENT. Should be cleaned with a spray cleaner, and blown dry.

More information, and some illustrations can be found doing a common search :

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