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John
John, Master A.S.E Automotive technician
Category: Chevy
Satisfied Customers: 9176
Experience:  A.S.E MasterTechnician A1-A8 w/L1,38 years experience General Motors Master Technician
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Chevrolet Impala LS 2003 3.8 WITH A PO171 CODE. LEAN FUEL

Resolved Question:

2003 3.8 WITH A PO171 CODE. LEAN FUEL BANK. IT HAS A BRAND NEW MASS AIR FLOW SENSOR. NEW PLUGS. GOOD CLEAN AIR FILTER. WHAT COULD BE THE PROBLEM ?
Submitted: 6 years ago.
Category: Chevy
Expert:  John replied 6 years ago.

Hello & Welcome to JA,

The powertrain control module (PCM) controls the air/fuel metering system in
order to provide the best possible combination of driveability, fuel economy,
and emission control. Fuel delivery is controlled differently during Open Loop
and Closed Loop. During Open Loop, the PCM determines fuel delivery based on
sensor signals, without oxygen sensor (O2S) input. During Closed Loop, the PCM
adds oxygen sensor inputs to calculate the short and long term fuel trim, fuel
delivery adjustments. If the oxygen sensors indicate a lean condition, the fuel
trim values will be above 0 percent. If the oxygen sensors indicate a rich
condition, the fuel trim values will be below 0 percent. The short term fuel
trim values change rapidly in response to the heated oxygen sensor (HO2S)
voltage signals. The long term fuel trim makes coarse adjustments in order to
maintain an air/fuel ratio of 14.7:1. If the PCM detects an excessively lean
condition, diagnostic trouble code (DTC) P0171 sets.

Your problem is very likely to be a leaking intake manifold gasket.

Customer: replied 6 years ago.

HOW WOULD THIS BE CONFIRMED? WOULD THE TEST BE COSTLY? AND IF IT

WAS CONFIRMED TO BE A LEAKING INTAKE GASKET, IS IT A COSTLY REPAIR?

Expert:  John replied 6 years ago.

It is a 2.0 labor hour job & 65.00 parts if plactic upper intake is ok,if not add 100.00

These intakes are bad about burning thru at the EGR valve. Using a spray can of carb spray (spraying in short bursts) around intake & watch 0/2 sensor,if voltage stays above .875 MV ,you found the leak.

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