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Ron, ASE Certified Technician
Category: Ford
Satisfied Customers: 33025
Experience:  23 years with Ford specializing in drivability and electrical and AC. Ford certs and ASE Certs
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I have a 2000 ranger. get codes p0171 and p0174. I changed ...

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I have a 2000 ranger. get codes p0171 and p0174. I changed MAF, EGR, DPFE Sensor. Fuel pressure is OK and I can''t find a vacuum leak. Vacuum is steady @ 15 inches but doesn''t go to zero when throttle is opened and only goes up to about 17 when closed, then back to 15.Haven''t checked compression yet. Will worn rings give me a lean code. IT doesn''t blow smoke or burn oil.
Submitted: 8 years ago.
Category: Ford
Expert:  Ron replied 8 years ago.


Thank you for asking your question on Just Answer

The common concern for the lean codes 0171 and 0174 is leaking intake gaskets. Ford has an upgraded gasket set and this leak will not effect vacuum reading as it is internal. Replacing the upper an lower gasket will correct you concern. But in some case it can be someting as simple as a bad MAF (mass air flow ) sensor) If you can run this test..

Check the Barometer (BARO) reading for indication of a potential Mass Air Flow (MAF) sensor issue.

Check Short Term Fuel Trim (STFT) readings with the engine running. If they are high at the time, nurse propane or carburetor cleaner around potential vacuum leakage points on the engine, and pinch the vacuum lines closed to see if the fuel trim readings drop, pinpointing the source of the leak.Normal BARO Hz reading is 155-159 Hz at sea level and drops about 3 Hz for every 1000 feet gained in altitude. The Powertrain Control Module (PCM) calculates the barometric pressure from the Mass Air Flow (MAF) sensor input under certain Wide Open Throttle (WOT) modes of operation. If the MAF is cleaned or replaced, perform an adaptive relearn on the PCM by disconnecting the battery negative cable. After reconnection, start the engine and monitor the fuel trim readings and BARO reading, during and after a test drive, to verify normal values and that the problem is repaired.

Ron and 2 other Ford Specialists are ready to help you
Customer: replied 8 years ago.
I've sprayed starting fluid all over the engine, cannot find any leaks
Expert:  Ron replied 8 years ago.
The leak will not show up on the out side of the engine. Its an internal leak and can only be repaired by replacing the upper and lower intake gasket as long as your sure the MAF is good. Im betting on the gaskets. A very common issue on this truck.

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