04 explorer 4.0 soho po171

Bought truck non running,found broken rear timing cassette.I pulled the motor bought the expensive cam alignment set and everything went well changed all the chains and cassettes.put it back in it fired right up but runs quite rough and only code on it is a po171 fuel trim lean on bank 1.Checked for vacuum leaks pulled the intake and valve covers rechecked the timing,all good.Compression on bank 1 is 170,165 and 170.

My car has 101000 miles.
My car has an automatic transmission.

Experienced mechanics share their insights in answering this question :
Hi there. The most common cause for the P0171 code is a vacuum leak. I would double check all vacuum line connections to eliminate this as the primary source of your issue. It is also possible that the intake manifold gaskets are leaking. Over time they get brittle and will not seal very well and will need to be replaced.The only other possible cause of this OBD-II trouble code is a MAF sensor or a oxygen sensor that is failing.

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Too much fuel and/or too little air results in the engine running rich setting a P0172 trouble code, while too little fuel and/or too much air results in the engine running lean resulting in a check engine light for the Ford P0171 code.
A P0171 code is set by your vehicle`s powertrain control module (PCM) when it detects that the air-to-fuel ratio of your vehicle is too lean. This means that the PCM is relaying that the engine is receiving too much air into the combustion chamber and not enough fuel.
A plugged Fuel Filter or poorly functioning Fuel Pump can set the P0171 code. The computer hears (accurately) from the Oxygen Sensor that the Fuel Mixture is too lean so the computer keeps increasing the amount of fuel being delivered into the combustion chambers.
You probably know that the answer the questions is — no! A P0171 or P0174 lean code with an O2 sensor reading lean all the time mean — well, several things. The real problem may not be a bad O2 sensor, but possibly be an engine vacuum leak, low fuel pressure or dirty fuel injectors that are causing the engine run lean.
P0171 is triggered by the engine bank 1 “upstream” oxygen sensor and P0174 is triggered by the engine bank 2 “upstream” oxygen sensor. The oxygen sensor alerts your system when the condition is too lean meaning there`s too much oxygen in the exhaust.
How Serious Is Code P0171? While it is common for a driver to only experience minor driveability problems when the P0171 trouble code is present, driving with this code can overheat the engine and cause internal engine damage.
What Does P0171 and P0174 Mean? DTCs P0171 and P0174 are generic codes that set when the feedback on the engine`s air/fuel mixture becomes too lean for the Engine Control Module (ECM) to correct within its normal operating range. A lean mixture is a mixture that has too much air or not enough fuel.
This code is a crankshaft position sensor failure. It would have nothing to do with the catalytic converter. It can cause issues with starting the vehicle and keeping the engine running, which may have an effect on the exhaust system. A failing cat can also cause stalling, so without the code, they could look similar.
P0171 is triggered by the engine bank 1 “upstream” oxygen sensor and P0174 is triggered by the engine bank 2 “upstream” oxygen sensor. The oxygen sensor alerts your system when the condition is too lean meaning there`s too much oxygen in the exhaust.
How Serious Is Code P0171? While it is common for a driver to only experience minor driveability problems when the P0171 trouble code is present, driving with this code can overheat the engine and cause internal engine damage.

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04 explorer 4.0 soho po171
ANSWER : Hi there. The most common cause for the P0171 code is a vacuum leak. I would double check all vacuum line connections to eliminate this as the primary source of your issue. It is also possible that the intake manifold gaskets are leaking. Over time they get brittle and will not seal very well and will need to be replaced.The only other possible cause of this OBD-II trouble code is a MAF sensor or a oxygen sensor that is failing.

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2013 Explorer rims on my 2003 Explorer
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When the car hits 40 mph it feels like it wants to stall and slow down.
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Throttle body position is at 40% at idle and I just replaced tbs
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