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I'm scratching my head as to what is causing this too lean code on my truck. 2013 F150 Supercrew 4x4 3.5 Ecoboost 74k miles. I've replaced the upstream O2 sensor and the PCV valve on the Bank 1 side, also replaced the MAP sensor by the air filter, I also cleaned the other two. Checked vacuum hoses, sprayed starter fluid on hose connections and checked for idle to no avail. I've heard of people using shop vac and putting it on the tail pipe to pressure up with air and check for leaks with soap and water which I had not tried. I've heard that the Intake valve which is electronically controlled tend to go bad on Ford trucks which might cause an excess of air inside. Also read that some of the fuel pumps or injectors go bad can cause this. On my scanner they seem t be running normal put afuel treatment through and didn't make a difference. I took it in at 10am and called at 5pm and they said the tech having problems pinpointing it....Anyone have this same issue? its only shooting out the bank 1 side
 

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Double check all vacuum hoses. Short term Fuel Trim looks not too bad... how is long term?
Also, what year is the truck?
Check Fuel Pressure (In tank pump, and mechanical)
Intake valves are not electronic, they are actuated by the camshafts
Our Ecoboost engines have variable cam timing on intake and exhaust, however they will not cause the valves to stay open.

Are there any other codes in the PCM?
 

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Might have replaced a bad O2 with a new bad O2. It happens.
Most likely o2, then injector problem or wiring problem at injector.
I would change O2 again, check injector pulse to rule out electrical, then pull and flow test injectors. <all 6>
What is the fuel pressure? Typically if it was either pump you would lean both sides but not at idle.
 

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Swap your O2 sensors. Left side to right side and vice versa instead of just buying a new one. If your problem switches sides...
 

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Discussion Starter #5
@noodles

No other codes in the PCM...it has been the only one. I did have another code pop up but it was a bad MAP sensor by the air filter. Replaced and code cleared.Other than that just P0171. The truck is a 2013 F150 Ecoboost XLT Supercrew 4x4 6.5 box.
 

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Swap your O2 sensors. Left side to right side and vice versa instead of just buying a new one. If your problem switches sides...
This^^^^.
 
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