code 0171

[Rons beast]

I have been getting CEL code 0171 intermittently for about 6 months, in my 96 5.0 Eddie Bauer. (about 156K) It used to come on, I would check and clear and it didn't show again for maybe a few weeks. About a month ago I started to get the same code more often. I checked for vaccuum leaks, and actually checked each vac line for leakdown, found nothing, checked the vac reserve tank, all good, checked the manifold for vac leaks, with a spray of carb cleaner, also nothing. I checked every nook and cranny for a leak....nothing.....agh!!!!

I read that the o2 sensors may be the problem so yesterday I changed both forward sensors, (in the exh manifolds ) I thought I had the problem solved, as I saw the sensor from the right bank, (bank 1)had substancialy more black residue on it compared to the sensor from the left bank, which was reddish gray in color.

Thought all was well then today after driving only about 12 miles the darn light comes on again.

HELP!!!!!

Any Ideas/

And if the right bank (bank1) is lean as the code suggests, why is the sensor coated with carbon, like it is rich?

Has any body else had this problem?

Any help Is welcome......thanks in advance.

 

[miesk5]

yo Ron,

DTC P0171 - System to Lean (Bank 1);

The Adaptive Fuel Strategy continuously monitors fuel delivery hardware. The test fails when the adaptive fuel tables reach a rich calibrated limit.

DTC P0171 & P0174 Lean Troubleshooting; "...These codes commonly occur on many Ford vehicles, and are set when the powertrain control module (PCM) sees the air/fuel mixture is running too lean (too much air, not enough fuel). Unmetered air can enter the engine through a vacuum leak, a dirty airflow sensor (MAF) that is not reading airflow accurately, an EGR valve is not closing (DPFE) and is leaking exhaust into the intake manifold, an EGR valve that is allowing too much flow (because the EGR differential pressure sensor that monitors EGR flow is faulty and is under-reporting EGR flow). If the problem is not enough fuel, the underling cause may be a weak fuel pump, restricted fuel filter, leaky fuel pressure regulator or dirty fuel injectors

MAF Contamination TSB 98-23-10 for 94-96 by Ford via miesk5 at cc SEE BELOW

Air leaks after the MAF. Check tubing from filter housing to TB. Is TB tight to manifold and gasket still looking good? Same for intake man gasket(s)

EGR system: Leaking gasket. Stuck EGR valve. Leaking diaphragm or EVR. Bad DPFE Sensor or it's hoses to EGR Tube (should have another code tho)

Vacuum Leaks. iggie for now - btw, get a vacuum gauge. Cheap and great diag. tool! Could have a leak inside cab for HVAC system.

PCV system. Ck elbows for cracks or loose connection.

Improperly seated engine oil dipstick.

Base Engine: Oil overfill.

Cylinder compression. Since you see the O2 Sensor has carbon... think it is really; An engine burning oil will turn the tip of the sensor a brownish color." see Contaminated Oxygen Sensor pics w/Diagnosis, General Source: by TomcoExhaust leaks before or near the HO2Ss

or

Since the oxygen sensor is exposed to high heat in the exhaust system to the car, the main contaminant likely to be present is a thick layer of baked carbon on the sensor tip, which doesn't dissolve easily in any solvents. So one way to clean O2 sensor with this carbon deposit is to heat the oxygen sensor tip with a blow torch (like propane). Expose the sensor tip to the torch till it's about to turn red, then dip the sensor tip quickly into water followed by cleaning the tip by blowing compressed air. This will make the carbon deposit to break free. We recommend repeating the procedure a few times until the carbon deposits are removed from the sensor tip.

by Eric D

=============

TSB

98-23-10 MASS AIR FLOW (MAF) - SENSOR CONTAMINATION - SERVICE TIP

Publication Date: NOVEMBER 10, 1998

Do you have any of these Symptoms?

Lack of Power

Spark Knock/Detonation

Buck/****

Hesitation/Surge on Acceleration

Malfunction Indicator Lamp (MIL) Illuminated - DTCs P0171, P0172, P0174, P0175 may be stored in memory

This TSB involves use of Ford Diagnostic equipt. (New Generation Star (NGS) Tester), so basic ck is visual MAF inspection esp w/the "forever" washable air filters that are over-oiled, altho some such as da K company now refuse to admit this is a cause.

So look here for cleaning the MAF