('06-'08) P0171 - Subaru Forester Owners Forum
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post #1 of 3 (permalink) Old 06-16-2019, 02:23 PM Thread Starter
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parad1mg's Avatar
Join Date: Jul 2009
Location: La Mirada CA
Posts: 389
Car Year: 06
Car Model: Forester
Feedback Score: 1 reviews

So, I've been getting this code intermittently and in the past week, it kept coming back after a few miles of driving.

Car is a 2006 forester X.

What has been done:

1. New denso O2 sensor.
2. New denso MAF.
3. Checked all vacuum lines, no leaks found.
4. New PCV valve and hose assembly.
5. Checked for exhaust leaks pre-O2, no leaks found.
6. Cleaned TB.
7. Checked intake box and flex hose for cracks, none found.

What should I check next? Injectors? Fuel pressure and pump?

Thoughts? Ideas?


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post #2 of 3 (permalink) Old 06-16-2019, 03:29 PM
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it is a bank 1 too lean run code,............. usually maf caused but it can be intake manifold leak, or head gasket, running this .if it is real and not false code ................ too long can cause excessive engine heat and ............. one of the problems is that it may only be the maf connector or 2ndary O2 sensor cleaning maf or map may not be enough and it may be replacement time,,.............. but check the wiring for the maf and do a compressions test on bank one at least , in rare cases, a camshaft that is having a lobe flatten out will not open the intake valve long enough to deliver the fuel fully and it can look like this condition

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post #3 of 3 (permalink) Old 06-16-2019, 03:32 PM
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and yes a weak or worn injector is also a cause for subes often,
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  Subaru Forester Owners Forum > Technical Forums and Vehicle Assistance > Engine and Exhaust > EJ25 - 2.5L Non-Turbo (1998-2010)

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