Learn to Diagnose Why Your Car is Stalling or Sputtering
When the car is running, it needs to be able to bring in air through the air intake and expel air out through the exhaust. If the engine is stalling, sputtering, or slowly accelerates even with the gas pedal pressed down, the airflow might be restricted. Bad or blocked parts like a dirty air filter or a clogged air inlet tube can cause engine performance issues like hard starting or rough idling. Checking the air intake system doesn’t take long. This article explains what to check if your engine isn’t performing as well or if a check engine light came on for the air intake system.
Symptoms of a Dirty Air Filter and Intake Problems
The following symptoms can appear with bad air intake parts, like a bad air filter or faulty mass air flow (MAF) sensor
- The engine tries to start but not easily (hard starting)
- Check engine light is on for intake system-related codes like the MAF sensor
- Whistling or chattering noises that sound like an object is restricting airflow
- Rough idle
- In extreme cases, engine misfires
- Reduced horsepower
The following symptoms can appear on older cars that don’t have computers but have air intake problems
- If you have a dirty air filter or it’s clogged, the engine will continue to burn fuel to keep running since there is no computer to monitor it
- Poor acceleration and less engine power
- Black smoke from the exhaust
Why Is Air Flow Restricted?
Inside the engine, the air/fuel ratio should be 14.7 parts of air for 1 part of fuel that’s burnt. If this mixture was off, the engine will run but there may be performance issues.
Clogged or Dirty Air Filter
The air intake system has an air filter to filter any debris that could clog the system.
- Check the engine air filter for any debris like leaves or dirt that may block airflow
- Check the air filter for damage or bending, which can cause air restrictions
- Look inside the air filter’s fins for excessive dirt. A bad engine air filter will look excessively dirty and may look dirty from a distance
A bad air filter needs to be replaced.
Clogged Air Inlet Tube
The air filter housing typically has an inlet leading to it. The inlet tube is usually placed along the front or the side of the engine compartment.
- Check the air inlet tube for damage or debris. If objects like a plastic bag are blocking the air inlet tube, the air intake system will have difficulty pulling in air.
Broken Air Intake Parts
The engine will have difficulty performing with broken parts in the air intake system, like a MAF sensor or an intake hose.
How to Test the Air Intake System with an Advanced Scan Tool
You can connect an advanced scan tool and stream data such as the engine speed and the amount of air drawn into the engine
- The RPM reading should spike and level out at idle
- The MAF rating should level out
In the case of restricted airflow, the MAF reading will be erratic from the inconsistent airflow.
Why Is My Engine in Limp Mode?
If there is a restriction in the air system, that can cause a check engine light, the car might go into limp mode. Limp mode decreases engine power and lets the driver pull over safely without causing permanent damage to the engine. If the engine goes into limp mode, pull over safely.
One thought to “Dirty Air Filter or Bad MAF Sensor?”
The tube that runs from air box to throttle body keeps blowing off pressure cap why?