2018 Lexus ES350 Has Rough Idle

Diagnosing the Causes of Rough Idling in Your 2018 Lexus ES350 and How to Restore Smooth Performance

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Reviewed by
Andrew Hajjar
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 2018 Lexus ES350 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 2018 Lexus ES350 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.

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.

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 2018 Lexus ES350?

When diagnosing a rough idle in a 2018 Lexus ES350, 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 air filter; a dirty or clogged filter can significantly restrict airflow, leading to performance problems. Following this, examine the spark plugs for wear or fouling, as these components are crucial for proper engine combustion. If the spark plugs are in good condition, turn your attention to the fuel system, checking for clogs in the fuel filter or issues with the fuel injectors. Additionally, inspect the vacuum hoses for any leaks or cracks that could disrupt the air-fuel mixture. Cleaning the throttle body is another vital step, as a buildup of dirt can hinder airflow. Finally, check for vacuum leaks using a smoke machine or carburetor cleaner, as these can also contribute to a rough idle. By following this structured diagnostic approach, you can effectively identify and resolve the underlying causes of a rough idle in your Lexus ES350.

What are the common problems that could cause a rough idle in a 2018 Lexus ES350?

When diagnosing a rough idle in a 2018 Lexus ES350, it's crucial to explore several common issues that may be impacting engine performance. A dirty or clogged air filter can significantly restrict airflow, leading to an uneven idle. Additionally, worn or faulty spark plugs are known to cause misfires, disrupting the combustion process and resulting in a rough idle. Vacuum leaks can also be problematic, as they disturb the essential air-fuel mixture needed for smooth operation. Fuel system issues, such as a clogged fuel filter or a malfunctioning fuel pump, can further complicate matters by affecting fuel delivery to the engine. Moreover, a malfunctioning Mass Airflow Sensor (MAF) can provide incorrect readings, exacerbating idle problems. Lastly, a faulty Exhaust Gas Recirculation (EGR) valve can interfere with combustion, contributing to rough idling. By identifying and addressing these common problems through regular maintenance and timely repairs, you can help ensure that your Lexus ES350 operates smoothly and efficiently.

How urgent is it to address the rough idle in my 2018 Lexus ES350?

Addressing a rough idle in your 2018 Lexus ES350 is not just a matter of comfort; it is crucial for the longevity and performance of your vehicle. A rough idle can indicate serious underlying problems, such as faulty spark plugs, fuel system malfunctions, or issues with the air intake. Ignoring these symptoms can lead to decreased fuel efficiency and engine misfires, which may escalate into more severe damage over time. For DIY enthusiasts, it’s essential to recognize that timely intervention can save you from costly repairs down the line. Regular maintenance checks and prompt repairs can help maintain your engine's health, ensuring that your vehicle runs smoothly and efficiently. If you notice a rough idle, consider conducting a thorough inspection or consulting a professional mechanic to diagnose the issue before it leads to significant complications. Taking action now can prevent safety risks and enhance your driving experience.

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2018 Lexus ES350 Rough Idle: Causes & Repair Costs