2021 Toyota GR Supra Has Rough Idle

Troubleshooting Causes of Rough Idle in Your 2021 Toyota GR Supra 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 2021 Toyota GR Supra has rough idle are a vacuum leak, an issue with the spark plugs, or a problem with the ignition coil.
  • Spark Plugs: Worn or fouled spark plugs can lead to misfires, poor fuel economy, and difficulty starting the engine.
  • 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 2021 Toyota GR Supra 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 are the steps to diagnose a rough idle in a 2021 Toyota GR Supra?

When diagnosing a rough idle in a 2021 Toyota GR Supra, it's essential to adopt a systematic approach that prioritizes simpler checks before delving into more complex diagnostics. Start by using an OBD-II scanner to check for any error codes, as these can quickly point you to specific issues within the vehicle's systems. Next, inspect the spark plugs for wear or fouling, as these components play a crucial role in engine performance. A clean air filter is also vital; ensure it is free from dirt and clogs that could restrict airflow. Following this, examine the vacuum hoses for leaks, which can disrupt the air-fuel mixture and lead to idling problems. Don't overlook the fuel system; check the fuel filter and injectors for clogs that could affect fuel delivery. Additionally, inspect the throttle body for carbon buildup, as this can hinder airflow and engine response. Finally, assess the exhaust system for any leaks or damage that could impact overall engine performance. By methodically following these steps, you can effectively identify and resolve the rough idle issue in your Supra, ensuring optimal performance.

What are the common problems that could cause a rough idle in a 2021 Toyota GR Supra?

When dealing with a rough idle in your 2021 Toyota GR Supra, it's essential to consider several common problems that could be at play. One of the first things to check is the air filter; a dirty or clogged air filter can significantly restrict airflow to the engine, resulting in an uneven idle. Additionally, inspect the spark plugs, as worn or faulty plugs can lead to misfiring, which is a frequent cause of rough idling. Another critical area to examine is the vacuum system for any leaks, as these can disrupt the air-fuel mixture and cause instability in engine performance. Fuel system issues, such as a clogged fuel filter or malfunctioning fuel injectors, can also contribute to a rough idle by affecting the engine's fuel delivery. Furthermore, the throttle body should be inspected for malfunctions, as it plays a vital role in regulating air intake. Lastly, consider the Engine Control Module (ECM); any sensor malfunctions or software glitches here can disrupt overall engine performance. By systematically addressing these potential issues, you can effectively diagnose and resolve the rough idle problem in your Supra, ensuring a smoother driving experience.

How urgent is it to address the rough idle in my 2021 Toyota GR Supra?

Addressing a rough idle in your 2021 Toyota GR Supra is crucial for both safety and performance. A rough idle often indicates underlying engine issues that, if left unresolved, can escalate into more severe problems, potentially leading to costly repairs. Ignoring this symptom may not only decrease your vehicle's fuel efficiency but could also compromise critical systems, posing safety risks while driving. Regular maintenance and prompt attention to such issues can prevent further complications, ensuring that your Supra operates smoothly and efficiently. Therefore, it is essential to prioritize diagnosing and fixing a rough idle to maintain the longevity and reliability of your vehicle.

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