2020 Lexus LC500 Has Rough Idle

Troubleshooting Causes of Rough Idle in Your 2020 Lexus LC500 and How to Restore Smooth Performance

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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 Lexus LC500 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 2020 Lexus LC500 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 2020 Lexus LC500?

To effectively diagnose a rough idle in your 2020 Lexus LC500, start with a systematic approach that prioritizes simpler checks before delving into more complex diagnostics. Begin by using an OBD-II scanner to identify any error codes that may indicate specific issues within the engine. This initial step can save time and direct your focus to the most likely culprits. 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 essential; ensure it is free from dirt and debris to maintain optimal airflow. Following this, check for vacuum leaks by examining hoses and connections, as any disruption in the air-fuel mixture can lead to a rough idle. Cleaning the throttle body is another important step, as carbon buildup can impede airflow. Additionally, assess the fuel system, including injectors and filters, to ensure they are functioning correctly. Finally, don’t overlook the PCV valve, as a malfunctioning valve can significantly impact engine performance. By following this structured diagnostic approach, you can effectively identify and resolve the rough idle issue in your Lexus LC500.

What are the common problems that could cause a rough idle in a 2020 Lexus LC500?

When dealing with a rough idle in your 2020 Lexus LC500, it's essential to consider several common problems that could be affecting your vehicle's performance. One of the first areas to check is the air filter; a dirty or clogged air filter can significantly restrict airflow to the engine, leading to an uneven idle. Additionally, inspect the spark plugs, as worn or faulty plugs can cause misfires, which are often felt as a rough idle. Another critical component to examine is the vacuum system; any leaks can disrupt the air-fuel mixture, resulting in instability during idling. Fuel system issues, such as a clogged fuel filter or a malfunctioning fuel pump, can also contribute to poor engine performance and rough idling. Furthermore, the Mass Airflow Sensor (MAF) plays a vital role in regulating the engine's air intake; if it's malfunctioning, it can cause the engine to run either too rich or too lean, leading to idling problems. Lastly, don't overlook the Exhaust Gas Recirculation (EGR) valve, as a faulty EGR can interfere with the combustion process, further exacerbating rough idle symptoms. By systematically addressing these potential issues, you can effectively troubleshoot and resolve rough idle problems in your Lexus LC500.

How urgent is it to address the rough idle in my 2020 Lexus LC500?

Addressing a rough idle in your 2020 Lexus LC500 is crucial for maintaining the vehicle's overall performance and reliability. Ignoring this symptom can lead to a cascade of problems, including decreased fuel efficiency and increased emissions, which not only affect your wallet but also the environment. Moreover, a rough idle may indicate underlying engine issues that could escalate into more severe damage if left unattended. By prioritizing timely repairs, you not only safeguard your engine's health but also enhance your driving experience. Regular maintenance and prompt attention to warning signs can prevent costly repairs down the line, ensuring that your Lexus remains in peak condition for years to come. Therefore, it is advisable to address any rough idle symptoms as soon as they arise to avoid compromising your vehicle's performance and longevity.

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Troubleshooting Rough Idle in 2020 Lexus LC500 | RepairPal