Question about 2001 Ford Econoline

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Have a van w/ code P0171 and pending P1131. Idea is MAf

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Although the p1131 code may lead you to think that the oxygen sensor is potentially at fault it is in fact acting correctly by confirming the lean burn code P0171. I confirm your diagnosis and start with the MAF after first doing a quick leak check on all vacuum lines etc. If you disconnect the electrical connection to the MAF the p0171 code will go away, but this is no fix. Remove and clean the MAF sensor with 'electrical cleaner spray'....this is a no residue spray consisting of alcohol and a dry cleaning solvent and really does a great job of dispersing oily deposits. DO NOT use carb choke cleaner spray it is a) too harsh and b) leaves a residue. The MAF sensor is fragile so try not to touch it. If you have to wipe it use a cotton bud soaked in electrical cleaner and wipe very gently.

Posted on Dec 29, 2010

  • Anonymous Dec 29, 2010

    Orig. Code was only P1131. Cleaned and reset comp. Drove it the drivability issue no change actual worse. Code read P0171 pending P1131. Ideas

  • Joseph Prosser Dec 29, 2010

    The ECU would respond to 'lean mix' message from the oxygen sensor by enriching the mix. If the sensor persists in detecting lean burn condition (P1131) then the engine must be taking in more un-metered air than can be compensated for by the ECU. Possible sources of air leaks are: open EVAP purge valve; loose PCV valve; disconnected or hole in vacuum line to the inlet manifold; loose fit of the manifold to the cylinder head; open EGR valve; brake servo pipe. Use WD40 to spray on areas suspected as leaking and if the engine immediately picks up speed this will confirm the leak.
    Try the trick of disconnecting the MAF and see what happens. If the MAF is unreading the amount of air entering then this will lead to the lean burn condition.
    Another idea would be to swap the oxygen sensors between exhaust manifolds and see if the fault transfers with the sensor change or sticks with bank one.


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P0171 suggests th van is running to lean on bank 1 is the cylinder bank on the RIGHT (passenger side) the plug may be defective or coil damage, no spark.

Is this a gas version or Derv / diesel ? I am assuming it's gas.

DTC P1131 indicates the system is correcting RICH for an overly LEAN condition. In english this means the car's computer is telling the fuel pump to use more fuel (running RICH) because the engine has a low air-fuel mixture (LEAN). The car is out of tune or the airflow sensor, (O2) Heated Oxygen Sensor are worn or are getting an incorrect reading.

So quite rightly it could well be the MAF sensor, and I would look there first. also, try cleaning it with carb cleaner before replacing it, and also look for any air leaks in pipes as again this could cause this.



Posted on Dec 29, 2010

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For faulty MAF Sensor operation to be your problem, I would expect that there
should also be a P0174 code. The combination of the P0171 and P1131 suggest
an Intake air leak, Vacuum hose leakage, or a problem with the PCV system. Check those three areas first.
With a 9 year old Econoline van, vacuum leaks are pretty common.

Posted on Dec 29, 2010

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Chevy Silverado error p1151

P1151 Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 2

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All of these p1131 p1151 p0171 p0174 codes indicate a problem with a lean condition. This engine is known for vacuum leaks, so before you start throwing oxygen sensors at the problem, it pays to perform some diagnostics.
Start by cleaning the MAF sensor. Spray the sensor with CRC MAF sensor cleaner. Next, check the plastic vacuum lines, especially where they meet with rubber boots. If they are cracked or the rubber is swollen, replace the line. Then check the rubber elbow that holds the PCV valve. That elbow is a know failure point. In fact, the entire PCV tubing is a trouble spot on these engines. (thanks Ford).
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