HI! My question is with my 2008 Ford Focus SE. it has 150000 miles and is automatic. I got the dreaded PO171 system too lean code. I dont hear any hissing sounds for vacuum leak. I changed the mass airflow sensor and the upstream O2 sensor. the idle is a lil rough but drives fine so far. One thing i noticed on my reader that long term fuel trim is 22.6 seems high I think I may need to do a bottle of fuel system cleaner. Any thoughts? Exhaust leaks? doesnt sound loud but not as quiet on idle.
I dont hear any hissing sounds for vacuum leak
That's not a very good test for vacuum leaks.
I changed the mass airflow sensor and the upstream O2 sensor.
Did they test as bad?
long term fuel trim is 22.6 seems high
It's very high. The simple stuff would be vacuum leaks, clogged fuel injectors, low fuel pressure. You can find other possible causes in the link below:
https://www.obd-codes.com/p0171
