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Questions and Answers

Ford Expedition P0171 & P0174

Q. Hello, I have a 1998 Ford Expedition, 5.4 liter, 4WD, 67,000 miles, K&N air cleaner. I have been getting diagnostic codes P0171 and P0174. I have done the following to address the problem:

Ford Expedition P0171 & P0174
  • Replaced the PCV valve
  • Replaced the fuel filter
  • Ran several bottles of fuel injector cleaner
  • Inspect each vacuum line for leaks/cracks
  • Cleaned the K&N air cleaner
  • Reseat the oil dip stick
  • Checked the gas cap

After doing the above, I erased the codes, but the check engine light came back on after 175 miles, 4 days of driving (and with the same lean condition codes). What's left? Tear out the EGR valve? BTW, the Ford runs PERFECT! One last thing, what is "bank 1"? Is it the bank with #1 piston? The "left" side of the engine? I considered myself a pretty good shade tree mechanic, lay it on me, I'll figure it out!


A. You and about 24,000,000 other people have the same problem.

See Ford Mass Air Flow Sensors.

Bank one is the cylinder one side.

Added 11/24/02

Hello Vince, I just wanted to drop you a line and tell you how I got rid of the diagnostic codes listed below. I simply unbuckled the air cleaner, exposing the MAF. I then sprayed the two wires in the throat of the MAF with aerosol electronic cleaner. I used Chemtronics brand but I'm sure any brand of "fast evaporating" non-residue spray will do.

After the spray job, I waited one minute or so for the cleaner to evaporate and reconnected the air cleaner. After buttoning up the air cleaner, I erased the codes, it's been 700 miles and the codes have not returned! I suspect I had an ultra thin coating of dust/oil on the MAF wires.

Since you mentioned (in your web site) that writers never give feedback after the repair, I just wanted to reverse this trend!


Thanks Mike, great tip!!!

Added 1/25/06

I had that same problem with the Mass Air Flow Sensor on my 1996 Ford Thunderbird with a 3.8 liter. But the car would only run sputtering about 5 mph for a few feet, then kick in and be okay for the rest of the day. When it finally got to the first two blocks at 5 mph, I took it in after I had changed the plugs, filters, and it did no good.

When my mechanic said $25.00 and I had expected $200.00 to $300.00, that doesn't happen very often, I thought he really just made an adjustment and it probably would still do it but not as bad. However, it ran like a new car! When he showed me what he did, he did take the MAF assembly apart and he cleaned very lightly the 2 wires with a Q-Tip and rubbing alcohol, saving the cost of even the electronic spray which can be about $5.00 to $8.00.


I think I would still go with the spray. Actually touching that very thin wire makes it risky. I would hate to break that wire and have to replace the whole MAF sensor.

Additional Information provided courtesy of AllDATA

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© 2003 Vincent T. Ciulla

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