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02 OBW L.L. Bean
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I am throwing code P0171

A little background. I have maybe put 20 miles on this car, but has 234k on it. Recently replaced the engine from a junkyard with 150k miles on it. Engine sat on shelf for 1-2 years. Put it in the car. Runs great, except was throwing p0171 and p0174. Forgot to swap over the old fuel injectors and I am thinking that they are slightly clogged. Did a little italian tune up on it (run it up to redline a bunch of times thinking this will maybe clear some clogs) and now I am not getting p0174, but the p0171 is still there. Going through the outback service manual I have ruled out: exhaust leak, intake leak, fuel pressure, coolant temp, intake manifold pressure. Leaves me with intake temp and fuel injectors. I can't see intake temp with my obd scanner.

Swapped out right bank fuel injectors and damper and the car runs, but if you touch the gas and let go, it dies. If you touch the gas slightly and bring it back down slowly, it wants to idle at sub 500 rpm or die, like you need to set the idle screw on older cars. Swapped back to the junkyard injectors and it idles/revs fine. Is there a learning period with the computer where now it is getting the correct amount of fuel, but the computer cant tell? Am I missing something here? Is my 02/wideband sensor taking a crap on this side?
 

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On the Super Mod Squad
2002 3.0 VDC Wag + 2018 2.5 Leg Ltd
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26,491 Posts
dirty MAP/ MAF ?

front o2 sensor makes codes like that, (and such do get old, dirty, and get worse).

$50-75 buys a new denso from rockauto or amazon. (parts stores overcharge for such things). I would think if things persist it will make for misfires and a p0420.


and you might start running this on the proper 93 octane with a plain can of $6 seafoam mixed into each full tank. (such will slowly melt any gummy crap out of the lines if any exists from old bad gas in the tank).
 
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Yes, there is a learning period for the idle. From my experience, they will seem to droop too low when coming down from an idle until the computer is able to properly trim the idle. It sometimes takes a bit of driving with them periodically coming to an idle to complete the learning process.

I have never seen the learning process cause a DTC. Provided that you have good fuel pressure, I suspect that you are getting unmetered air in the intake from a vacuum leak. Are you able to check the fuel trim and compare the voltages from the O2 sensors?

What engine do you have?
 
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