How do I find out what to fix on a engine code P0171 on a 2002 Ford Escort?

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Mike Jetland

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My 02 Escort sedan is coming up with an engine code P0171 (bank 1 running lean). The service engine soon light is on. The idle is rough and my gas mileage has suffered. I did replace spark plugs within the last 7,000 miles as well as replacing both oxygen sensors and the mass air flow censor 3 times. I don't know what to have replaced?
When I spray MAF, do I spray the whole piece or just the black sensor part?
Do I disconnect both the positive and the negative or just the negative?
 
after replacing the sensors you needed to reset the computer that way the system will recognise the new items.. ( been down that road before) Normally an HO2S sends out a voltage signal from .1V to .9V, or lean to rich. If the PCM gets a lean signal from the HO2S it will richen the fuel mixture to compensate. And if it gets a rich signal, it will lean out the mixture. The computer is looking for the ideal voltage signal of .5V from the HO2S.

Fixing The Problem...
To confirm this disconnect the MAF sensor connector. This puts the vehicle into Failure Mode and Effects Management (FMEM). In FMEM mode, airflow is inferred by using rpm and throttle position instead of reading the MAF sensor. (In addition, the BARO value is reset to a base/unlearned value.) If the lean driveability symptoms go away, the MAF sensor is probably contaminated and should be replaced. If the lean driveability symptoms do not go away the MAF sensor is probably not contaminated.

When this happens Ford says you must replace the MAF since they cannot be repaired. With a dealer cost of about $177.00 and about 1.5 hours of labor the repair is not very expensive. However Ford is not correct. This problem can be fixed and it can be done by just about anyone.

What you need to do is go to the local Radio Shack and get a can of spray tuner cleaner, #64-4315. Disconnect the NEGATIVE battery cable and remove the MAF from the vehicle. Spray the inside of the MAF with the tuner cleaner. Be very careful when you spray the hot wire. It is very thin and if it breaks, you will have to replace the MAF. Clean it well and let it air dry for 15 or 20 minutes.

Don't use carburetor or brake cleaner. They leave a residue and you will be right back where you started. Use ONLY the tuner cleaner, which dries residue free. When it's dry put it back in the vehicle and reconnect the NEGATIVE battery cable. You will need to drive the vehicle several miles to let the PCM "relearn" your specific driving conditions. Once that is done the codes will not come back and you should notice all the symptoms are gone as well.

try this take your time it does work
 
check the mass air flow sensor, see if those little wires are intact, also try to reset the computer.
 
The codes I hear about most from Ford owners are P0171 or P0174; Fuel system lean, Bank 1 or 2. Now these codes indicate the engine is not getting enough fuel. This can be due to several factors, a bad Coolant Temperature Sensor (CTS), vacuum leaks or dirty injectors, among other things. One or more of the following symptoms accompanies these codes:

Lack of Power.
Spark Knock/Detonation.
Bucking and/or Jerking.
Hesitation or Surge on Acceleration.
 
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