Car Stalls While Driving? How to Diagnose and Fix

If you notice your car stalls while driving, this article and video reviews some parts you can inspect to see what could be the cause. You could have an issue with the throttle body. While the throttle body usually turns on the check engine light if it has an issue, this isn’t always the case, and we’ll show you what to look for and what to do to tell if it’s making your engine stall.

Parts to Inspect If Your Car Stalls While Driving

1A Auto mechanic holding a throttle body, which is a common cause for a car that stalls while driving

1. Air Intake Parts

Air needs to flow to the mass air flow sensor and into the throttle body and engine. If your car stalls while driving, you’ll want to check the airflow and how air enters the engine. An air filter is in the air filter housing. Make sure the housing is secured tightly and all the air intake hoses are connected and in good condition.

2. Throttle Body

Throttle body blade with excessive carbon build-up
Throttle body blade with excessive carbon build-up

The throttle body has a flap that opens and closes to reduce or increase airflow to the engine. Carbon can build up on the front and back of the flap. This build up can cause problems for the computer where it doesn’t know how to compensate. This can cause conditions like engine stalling that may happen without a check engine light, and it could affect your fuel mileage. The flap won’t open and close as smoothly, and there will be less airflow.

Symptoms of a Bad Throttle Body

  • Engine stalling
  • Less gas mileage
  • Check engine light

How to Diagnose the Throttle Body

Steps to diagnose the throttle body

  1. Check the Throttle Body for Carbon Build-Up

    To fix a throttle body with carbon build-up, you can replace or clean the throttle body. To remove the throttle body, you’ll need to remove the air filter housing, disconnect the air intake tube from the throttle body, and remove the bolts from the throttle body and disconnect the electrical connector.

  2. Clean the Throttle Body

    When cleaning the throttle body, you don’t want to move the blade manually, and you’ll want to clean the carbon off the back of the flap. If you’re cleaning the front side of the flap, you might have to slightly move the blade to clean the edges. It’s important to know that moving the blade can cause an issue with your vehicle’s performance. The throttle body’s motors and gears are sensitive, and moving the blade can prevent the throttle body from calibrating correctly.

    When using throttle body cleaner, be aware of the seal on the throttle body. If cleaner leaks past the seal and into the electronics, they can damage the throttle body and cause more drivability issues. Hold the throttle body at an angle or with the motor facing up and avoid directly spraying into the area with the seal.

    What Kind of Cleaner Should I Use to Clean the Throttle Body?
    We recommend using carburetor cleaner instead of brake parts cleaner since it won’t evaporate as quickly. A toothbrush works great to clean off the carbon. It will take some time to clean, and you’ll want to clean both sides of the throttle body blade.

  3. Complete an Idle Relearn Procedure

    After the throttle body is cleaned and reinstalled, or if the throttle has been replaced, you’ll need to complete an idle relearn procedure. On most vehicles, you’ll need to start the car and run it for about three minutes, shut it off for one minute, and start and run it for another three minutes. The idle might be really high for the first run, and by the end of the total 7 minutes, the idle should return to normal RPM levels.

    You can also complete an idle relearn procedure with a scan tool that’s capable. You’ll go into the scan tool, select “idle relearn procedure,” and follow directions on the scan tool.

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Car Stalls While Driving? - Expert Tips to Diagnose & Fix - 1A Auto
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Car Stalls While Driving? - Expert Tips to Diagnose & Fix - 1A Auto
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Follow the tips from our expert mechanics in this article and video if your car stalls while driving. You'll find out what can cause engine stalling and how to diagnose and fix it yourself.
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1A Auto
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