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Is my engine running too lean ?

Possible Reasons For My Customers Engine Running Lean

FEBRUARY 1, 2014 By POWERTRAIN PRO

 

Lean operation happens when there’s too much air in the air-fuel mixture. In minor instances, it won’t cause much problem, but in serious situations, it can cause massive headaches and expensive repairs. It might even lead to the need for engine replacement if left unchecked for a long period of time, thankfully there are many used engines for sale. Diagnosing a lean condition can be tough, as there are many different situations that can lead to it. Here are some of the most common reasons for an engine running lean.

Oxygen Sensors

Oxygen sensors are important parts of the exhaust system and play a vital role in reducing emissions. However, they’re responsible for more than that. The data sent from the car’s oxygen sensors to the computer helps it adjust the air-fuel mixture for optimal operation. If a sensor is bad or failing, the computer won’t be able to adjust this mix correctly. This can lead to either lean or rich operation, both of which are bad.

Fuel System Situations

One of the most common situations causing lean engine operation involves fuel system problems. Clogged fuel filters are the usual culprit (both inline and in-tank). If the filter becomes clogged, the amount of fuel flowing to the engine is reduced. That results in a low ratio of fuel to air, causing lean operation. Clogged fuel injectors can also cause this problem.

Airflow Sensors

All vehicles use what’s called an airflow sensor to determine just how much air is getting to the engine from the intake. If the sensor is going out or already failed, too much air might be entering the engine and causing lean operation. If the sensor is operating correctly, it tells the computer to increase fuel flow to compensate for additional airflow. If that doesn’t happen, it can cause real issues.

Most causes of lean operation are pretty easy to diagnose and require very little time. For instance, a failed oxygen sensor is usually diagnosable by checking the code causing a check engine light to illuminate. However, there are other issues that aren’t quite so easily diagnosed. Air leaks (vacuum leaks) in the engine fall into this category. Holes in hoses can cause too much air to enter the combustion system and make the engine run lean.

Lean operation is usually not a cause for engine replacement, but if you have an engine running lean for a long period before the customer brings it to your attention, real damage can be caused.