What does it mean by your Ford Taurus Mercury Sable engine is running lean?

A "lean" engine in your Ford Taurus or Mercury Sable (both share similar engines across model years) means the air-fuel mixture entering the combustion chamber has too much air and not enough fuel. Instead of the ideal, stoichiometric ratio (roughly 14.7 parts air to 1 part fuel), the mixture is significantly richer in air.

This condition can stem from several issues:

* Mass Air Flow (MAF) Sensor Problems: This sensor measures the amount of air entering the engine. A faulty MAF sensor can send incorrect readings, leading the computer to inject less fuel than needed.

* Fuel Injectors: Clogged or failing fuel injectors may not deliver sufficient fuel, resulting in a lean condition.

* Fuel Pump Issues: A weak fuel pump might not supply enough fuel pressure to the injectors.

* Vacuum Leaks: Leaks in the intake system allow excess air to enter, upsetting the air-fuel ratio.

* Oxygen Sensor (O2 Sensor) Problems: The O2 sensor monitors the exhaust gases and provides feedback to the engine control module (ECM) to adjust the air-fuel mixture. A faulty sensor can lead to inaccurate adjustments, causing a lean condition.

* Fuel Pressure Regulator Issues: This regulates the fuel pressure to the injectors. A malfunctioning regulator can lead to insufficient fuel pressure.

* EGR Valve Problems (Exhaust Gas Recirculation): A faulty EGR valve can cause a lean condition, although it's less common than the other problems listed.

A lean-running engine can cause several problems:

* Reduced Engine Power: The engine might feel sluggish or lack power.

* Overheating: Incomplete combustion due to the lack of fuel can generate excessive heat.

* Misfires: The lean mixture can lead to misfires, causing rough running and potentially damaging the catalytic converter.

* Damaged Catalytic Converter: The high temperatures from incomplete combustion can damage the catalytic converter.

* Check Engine Light: The check engine light will likely illuminate, accompanied by diagnostic trouble codes (DTCs) that can help pinpoint the specific problem.

It's crucial to get your Ford Taurus or Mercury Sable diagnosed by a mechanic as soon as possible if you suspect a lean condition. Driving with a lean engine for an extended period can cause significant and expensive damage. They will use a scan tool to read the diagnostic trouble codes and perform further tests to determine the root cause.