Severity: Fix within days. Drive with caution and watch for new symptoms.
The engine is getting too much air or too little fuel on bank 1, so the exhaust has more oxygen than it should. The computer has already added as much fuel as it can to compensate.
Clean the mass air flow sensor, check all vacuum and PCV hoses for cracks, and check fuel pressure before replacing sensors.
You may feel hesitation or a rough idle. A lean engine can run hot, so get it checked soon and avoid hard acceleration.
You can drive short distances carefully; watch for worsening symptoms. You may feel hesitation or a rough idle. A lean engine can run hot, so get it checked soon and avoid hard acceleration.
The most common causes are: Vacuum leak after the air-flow sensor; Dirty mass air flow sensor; Cracked vacuum or PCV hose; Weak fuel pump or clogged fuel filter; Failing oxygen sensor; Exhaust leak before the first oxygen sensor. A scan tool and a visual check of the parts above is where a technician starts.
Clean the mass air flow sensor, check all vacuum and PCV hoses for cracks, and check fuel pressure before replacing sensors.
