1999 Mercury Mountaineer 5.0 with a P0171 and P0174 DTC in memory. This is a great video on using fuel trim and freeze frame data to determine the cause of the lean condition.

Engine Performance Diagnostics chapter 4 pages 1219

Symptoms
low power
lean exhaust trouble codes P0171 and P0174
pinging
hesitation
surging

Fix
replace fuel pump and fuel filter

Tests shown
how to determine MAF sensor condition using BARO HZ data
how to use freeze frame data to determine type of lean condition
how to use STFT and LTFT at different loads to determine type of lean condition
how to test fuel pressure with a gauge
how to determine fuel delivery design
how to measure fuel pump current with a scope
how to locate the fuel pump inertia switch
how to calculate fuel pump RPM

Tools used
scan tool
fuel pressure gauge
Picoscope
inductive low amp probe

Playlist
(Chapters 14, 15,16) Fuel Delivery and Fuel Pressure Testing
   • (Chapters 14, 15,16) Fuel Delivery an...  

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