Codes P0171 and P0174, truck idling for a few minutes, then runs sporadic and idle drops

Tiny
JAY DEE2
  • MEMBER
  • 2003 FORD F-150
  • 5.4L
  • V8
  • 2WD
  • AUTOMATIC
  • 233,400 MILES
Truck listed above is an HD supercharged.
While stopped and idling for a period of 2 minutes or more the truck begins to run rough and the check engine light comes on. Once I accelerate, the truck runs fine until stopped for another 2 minutes or so. The check engine light will clear once the battery is disconnected, but will return once idling for a period.
Codes given are p0171 and p0174; system lean on bank 1 and 2.
Actions: fuel pump replaced (needed it), IAC, ERG, PCV, mass air meter, air filter, replaced vacuum lines that were faulty, spark plugs and coil packs done, o2 sensors replace today. Engine light comes back on after a short drive, idle goes to heck after about 2 to 3 minutes of idle running.
Help please. Only thing left I didn’t touch was intake gasket.
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Friday, March 20th, 2020 AT 3:20 PM

2 Replies

Tiny
BMDOUBLE
  • EXPERT
I think your hunch is right, Intake gaskets! Easiest way to verify this is to monitor the O2s11 and O2s21 sensor data while spraying the intake where it bolts down along the edges. If the voltage spikes to near one volt you have verified intake gasket leak!
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Friday, March 20th, 2020 AT 5:52 PM
Tiny
JAY DEE2
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BMDouble, thanks, will get on that first daylight.
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Friday, March 20th, 2020 AT 7:37 PM

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