2020 Toyota Corolla Has Rough Idle

Common Causes of Rough Idling in Your 2020 Toyota Corolla and How to Resolve Them

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Reviewed by
Bo Fader
Written by RepairPal Car Genius
Updated January 14, 2025
0%
21% chance it's the
Spark Plugs
0%
15% chance it's the
Ignition Coil
0%
64% chance it's
Something else
The most common reasons a 2020 Toyota Corolla has rough idle are a vacuum leak, an issue with the spark plugs, or a problem with the ignition coil.
  • Spark Plugs: A worn or fouled spark plug can cause misfires, rough idling, and decreased fuel efficiency due to incomplete combustion.
  • Ignition Coil: A faulty ignition coil can cause misfires, rough idling, and difficulty starting the engine due to inadequate spark delivery to the spark plugs.
Proper diagnosis will determine the exact cause of your symptom, saving you money on unnecessary repairs. The diagnostic experts at RepairPal Certified shops have the right tools and experience to solve any symptom.

How much does it cost to fix a 2020 Toyota Corolla has rough idle?

Common Repairs

The total repair cost will vary based on the condition of your vehicle and the number of repairs needed to fix your symptom. Proper diagnosis will save you money by finding the exact repairs needed to fix your car right the first time.

Brake caliper failure occurs in two different ways, and they create different symptoms.

The caliper can become stuck, in which case it won't release the brake pads. The seized caliper will cause the vehicle to brake constantly on one side, forcing the car to move toward that side. This pulling will be accompanied by a strong odor from one wheel.

Another way calipers fail is by leaking. If the caliper leaks, the brake pedal will feel too easy to push, and will sink all the way to the floor when held. Braking will become less effective the longer this goes on. There may also be brake fluid leaking onto the wheel.

Here are a few common symptoms of worn-out brake pads:

  1. Low brake pad warning light is on: Not all vehicles are equipped with this system, but if yours is, this dashboard indicator light will likely be the first signal it’s time to replace your brake pads.
  2. Brakes start to squeal regularly: This is often one of the first signs of worn brake pads and is caused by a metallic piece built into brake pads for this exact purpose. This part contacts the brake rotor to make a squealing or whining noise when the pads are low.
  3. Brakes make loud grinding noise: If not addressed early enough, your brake pads may get so worn that the metal backing plate of the pad grinds against the metal rotor.
  4. Brake pads look thin: You may be able to visually check your brake pad thickness to determine if they need replacement.

Brake rotors are mainly maintenance free, but when they have been subjected to abnormally hard use, the heat they absorb can cause the metal to turn blue, and cracking to occur. When this occurs, customers often specify they have lost braking power, or the vehicle's brakes are making noise. There may be no symptoms at all related to changing the brake rotors, since it is recommended to change brake rotors on most modern vehicles when performing a standard brake service.

Most often, a brake system inspection will just be a routine portion of manufacturer specified maintenance, and will be performed at mileage intervals. In those cases, there will likely be no symptoms. However, when a brake system makes a funny noise, causes vibration, is hard to use, will not slow the vehicle, prevents the vehicle from driving, makes the vehicle pull to one side, or leaks brake fluid, the vehicle will need a visit dedicated to the inspection of the brake system.

What diagnostic steps should be taken to address the rough idle in a 2020 Toyota Corolla?

When tackling a rough idle in your 2020 Toyota Corolla, it's essential to adopt a methodical diagnostic approach. Begin by inspecting the spark plugs, as worn or fouled plugs can significantly affect engine performance and lead to rough idling. Next, check the air filter; a clogged filter restricts airflow and can cause similar issues. Following this, examine the fuel injectors for any signs of clogs or malfunctions, as they are vital for delivering the correct fuel mixture to the engine. Additionally, look for any vacuum leaks in the intake system, which are common culprits of rough idling. If these initial checks do not resolve the issue, proceed to scan for trouble codes using an OBD-II scanner, as this can reveal specific problems related to the mass air flow sensor or throttle position sensor. Lastly, if the problem persists, consider consulting a professional mechanic for a thorough inspection, as they can provide insights that may not be apparent through DIY diagnostics. By following this structured approach, you can effectively identify and address the root cause of the rough idle in your Corolla.

What are the common problems that could cause a rough idle in a 2020 Toyota Corolla?

When experiencing a rough idle in your 2020 Toyota Corolla, several common problems may be at play. One frequent culprit is vacuum leaks, which can disrupt the air-fuel mixture and lead to unstable engine performance. Ignition coil and spark plug issues are also prevalent, as faulty components can cause misfires that result in a rough idle. Additionally, problems with fuel injectors or a dirty air filter can hinder proper fuel delivery and airflow, exacerbating the issue. The mass airflow sensor (MAF) plays a crucial role in measuring the air entering the engine; if it becomes dirty or faulty, it can lead to erratic idling. Other potential causes include a malfunctioning idle air control valve, throttle position sensor issues, or even problems with the head gasket. For those who are more mechanically inclined, checking these components can be a rewarding DIY project, but it’s essential to approach the diagnosis methodically. If the problem persists, consulting a professional mechanic may be necessary to ensure accurate identification and repair of the underlying issue.

How urgent is it to address the rough idle in a 2020 Toyota Corolla?

Addressing a rough idle in your 2020 Toyota Corolla is more urgent than it may initially seem. While it might not present an immediate emergency, neglecting this symptom can lead to significant engine problems over time. A rough idle often signals underlying issues such as misfiring, which can decrease fuel efficiency and potentially damage critical engine components. Common culprits include worn spark plugs, clogged fuel injectors, and air filter obstructions, all of which can exacerbate the rough idling condition if left unchecked. Furthermore, these issues can lead to poor combustion, affecting your vehicle's overall performance and reliability. By addressing the rough idle promptly, you not only enhance your driving experience but also prevent costly repairs down the line. Therefore, it is advisable to have a professional mechanic diagnose and resolve the issue as soon as possible to maintain your Corolla's optimal performance and longevity.

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2020 Toyota Corolla Rough Idle Causes & Repairs | RepairPal