98 Explorer 4.0 codes

[5.0Flareside]

Hey i got a check engine light came on the other day... read the codes off...

code P0171.. the online resource says either O2 sensor maf sensor issues, cyl misfire, or lean issue...

it feels like a slight missfire... is there anything in particular to look for?

 

[blacksnapon]

H41 DTCs P0172, P0171, P0174 AND P0175: FUEL SYSTEM AT THE CORRECTED FUEL TRIM
Diagnostic Trouble Codes (DTCs) P0171 bank 1 (Cylinder 1) and DTC P0174 bank 2 indicate the fuel/air ratio is too lean. The fuel trim system is at the rich correction limit.

DTC P0172 bank 1 and DTC P0175 bank 2 indicate the fuel/air ratio is too rich. The fuel trim system is at the lean correction limit.

DTCs HO2S Reference list:

HO2S-11 = DTCs P0171 and P0172
HO2S-21 = DTCs P0174 and P0175
Possible causes:

Fuel system

Excessive fuel pressure.
Leaking fuel injector(s).
Leaking fuel pressure regulator.
Low fuel pressure or running out of fuel.
Contaminated fuel injector(s).
Vapor management valve (VMV) leaking.
Induction system

Air leaks after the MAF.
Vacuum leaks (vacuum lines and gaskets).
Restricted air inlet.
PCV system.
Fuel purge system.
Improperly seated engine oil dipstick.
EGR System

leaking gasket.
Stuck open EGR valve.
Leaking diaphragm.
Base engine

Oil overfill.
Cam timing.
Cylinder compression.
Exhaust leaks before or near the HO2S(s).
Check intake air system for leaks, obstructions and damage.
Check air cleaner element, air cleaner housing for blockage.
Verify integrity of the PCV system.
Check for vacuum leaks.

 

[blacksnapon]

po171 is lean bank 1. Also check for vacuum leaks, particularly on bank 1. Lower intake o-rings are prone to failure on these engines.

 

[5.0Flareside]

ok.. is it typical for it to just suddenly pop up? i mean it was just one day and it was all of a sudden doing this..

 

[blacksnapon]

ok.. is it typical for it to just suddenly pop up? i mean it was just one day and it was all of a sudden doing this..

With all due respects, how else is it going to show?