Just purchased my Ranger last week at an auction. Decided to do the normal maintenance, oil change, air filter etc. Approx 1 hours after changing the air filter I see a check engine light. Scanner showed P0171 code....System too lean bank 1.....idle is perfect so not concerned with a vacuum leak. Will clean the MAF sensor tonight, but will also be checking real time stats later on the O2 sensors. Any other items I should check??

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2003 3.0 (160.000) all stock

Welcome to the site.

(Thread moved to the 3.0 section due to it being 99% related to a tech question).

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Curent 2003 Ford Mustang Mach 1 owner - Build Thread for her: Logan's 2003 Mach 1

Former 2003 Ford Ranger owner - Build Thread for her: Project Budget Buster

Just a quick update. Still seeing the same codes which point to oxygen sensor bank 1. Replaced all 3 oxygen sensors (Upstream and Down) but still see the same error codes. Another owner claimed it was a possible cylinder head issue, since ford outsourced the heads to the Soviet Union. sounds like a good story, but unable to validate. Any ideas of what the problem could be? I have to get the smog check next month, and with the engine light on it will not pass. I've removed the error code with my scanner, but the code will come back on within a few minutes. I also know it's not an intake leak as I've sprayed every component and all areas with starter fluid, and no change of idle....????

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2003 3.0 (160.000) all stock

Could be a few things. Did you check to make sure the MAF is clean, plugged in or or didn't accidentally break a wire? Have you changed the fuel filter and run some cleaner through the gas? Could be dirty there. It also wouldn't hurt to check the fuel pressure. I'm not sure how you would check it, but maybe the DPFE sensor is bad. I know you said you can't find a vacuum leak, but if it's not any of those, there might be a line cracked that you can't see enough to spray. There is a hidden hose under the manifold that you might have no sprayed. I recommend checking out this post

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Project log

99 Ford Ranger XLT Sport 3.0L
Autobot name:Rubeo Bestia(latin for little red beast)
135 amp alternator, 4.0 air intake tube, air box mod, 235/75-15 Hankook Dynapro, 01-03 conversion, buggman LEDs, throttle cable mod
I take photos for fun

You mentioned checking real time stats, do you have a device to monitor long term and short term fuel trims? If you monitor the fuel trims and increase the engine speed via throttle then a small vacuum leak would show improvement at higher RPMs and a fuel delivery problem should get worse.

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2000 Mazda B3000 Manual 5 speed