Both Banks have lean codes 5.4L 2002 F-150
01-10-2015, 02:00 PM
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Both Banks have lean codes 5.4L 2002 F-150
Okay so i know there are 1,000+ posts of lean codes but here's mine. I have lean codes thrown mostly on cold days. Fuel trims drop to normal under a load and raise to the mid 20s at idle/slow speeds. It seems to run very well open loop when its cold (very smooth) but developes rough idle when it warms a bit (closed loop). I have replaced all vacuum hoses that looked bad, the pcv valve and boot, MAF, spark plugs, and upstream O2 sensors. Doesn't seem like its an injector or coil problem because it runs smooth open loop...intake manifold/gasket leak? help me kind ladies or gentlemen
01-10-2015, 08:40 PM
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P0171, p0174, i looked at all the vacuum hoses today and cleaned the throttle plate real well. so if the problem still exists does it mean the intake manifold gasket or the manifold itself is most likely bad?
Last edited by michealleeward; 01-10-2015 at 09:14 PM.
01-10-2015, 09:43 PM
#4
Fuel pressure could be low too... My 2000 has a schrader valve on the passenger's side fuel rail for a convenient check.
Running strong in open loop then weaker in closed loop seems to indicate upstream O2 sensor that you replaced. Was O2 connector clean and solid?
Running strong in open loop then weaker in closed loop seems to indicate upstream O2 sensor that you replaced. Was O2 connector clean and solid?
