After replacing the head gasket code P0171 appeared

2012 TOYOTA PRIUS
205,000 MILES • 1.8L • 4 CYL • 2WD • AUTOMATIC
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BCMULLEN95
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I recently replaced the head gasket. No previous codes where present prior to the replacement of the head gasket. Now I show code p0171. Any ideas of how to best diagnose where I may have a leak or if it is the O2 sensor?
Feb 8, 2021 at 3:19 PM
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JACOBANDNICKOLAS
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Hi,

The code indicates a lean fuel mixture. I have a feeling there is a vacuum line/hose that was missed.

Let's check for that first. Here is a link that explains how to find a leak:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Do this and let me know what you find.

Take care and God Bless,

Joe
Feb 8, 2021 at 5:43 PM
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BCMULLEN95
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Sprayed all the vacuum hoses and intake, no engine acceleration noticed.
Feb 10, 2021 at 1:56 PM
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BCMULLEN95
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I also have permanent codes P0300, P0301, P0302, and P0117. New spark plugs, new ECT, new Water pump, new thermostat, and new coil packs. Not sure if they have anything to do with the P0171. I plan on driving the car through a drive cycle to see if the other permanent code clear.
Feb 10, 2021 at 2:00 PM
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JACOBANDNICKOLAS
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Hi,

A misfire shouldn't be a permanent code. Are you able to clear it? If so, clear all codes and drive it to see what happens.

Let me know what happens.

Joe
Feb 10, 2021 at 6:42 PM
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BCMULLEN95
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I should take it out for a drive tomorrow. I will let you know what happens.
Feb 11, 2021 at 10:11 PM
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BCMULLEN95
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Took it for a drive and it sound bad. It has a really rough idle. Could being off 1 tooth on the timing cause the same codes that I have regarding misfire?
Feb 12, 2021 at 12:03 PM
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JACOBANDNICKOLAS
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Hi,

Could you record it running and upload it for me to hear? When you put things back together, are you sure timing was correct?

Let me know.

Joe
Feb 12, 2021 at 3:27 PM