2004 Honda S2000 Has Rough Idle

Common Causes of Rough Idle in Your 2004 Honda S2000 and How to Resolve Them

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Reviewed by
Devin Cabugcal
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 2004 Honda S2000 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 2004 Honda S2000 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 2004 Honda S2000?

To effectively diagnose a rough idle in your 2004 Honda S2000, start with a systematic approach that prioritizes simpler checks before delving into more complex diagnostics. Begin by inspecting the spark plugs, as worn or fouled plugs can significantly impact engine performance. Next, examine the air filter; a dirty or clogged filter restricts airflow, which can lead to rough idling. Following this, check the vacuum hoses for any cracks or leaks, as these can disrupt the air-fuel mixture. It's also essential to assess the fuel system, ensuring that the fuel filter and injectors are functioning correctly. Cleaning the throttle body is another critical step, as carbon buildup can hinder idle quality. Utilize an OBD-II scanner to identify any error codes that may point to underlying issues. Additionally, inspect the idle air control valve, which regulates idle speed, and check the EGR valve for proper operation, as a malfunctioning valve can contribute to rough idling. By following this structured diagnostic approach, you can effectively identify and resolve the rough idle issue in your Honda S2000.

What are the common causes of a rough idle in a 2004 Honda S2000?

When dealing with a rough idle in your 2004 Honda S2000, it's essential to consider several common problems that could be at play. One of the first areas to check is the air filter; a dirty or clogged filter can significantly restrict airflow, leading to an uneven idle. Next, inspect the spark plugs, as worn or faulty plugs can cause misfires, which are often felt as a rough idle. Additionally, vacuum leaks can disrupt the air-fuel mixture, so examining the vacuum system for any leaks is crucial. Fuel system issues, such as a clogged fuel filter or a malfunctioning fuel pump, can also impact engine performance and contribute to rough idling. Another component to consider is the Idle Air Control Valve (IACV); if this valve is malfunctioning, it can lead to irregular idle speeds. Lastly, don’t overlook the throttle body, as carbon build-up can hinder airflow and exacerbate idle issues. By systematically checking these components, you can effectively diagnose and address the rough idle in your S2000, ensuring smoother engine performance.

How urgent is it to address the rough idle in a 2004 Honda S2000?

Addressing a rough idle in your 2004 Honda S2000 should be treated as a priority, as it can indicate underlying engine problems that may escalate if left unattended. A rough idle not only affects the vehicle's performance but can also lead to decreased fuel efficiency and increased emissions, which are both detrimental to your driving experience and the environment. Minor issues, such as dirty fuel injectors or worn spark plugs, can often be resolved with simple maintenance, but ignoring these symptoms could mask more serious problems like faulty sensors or engine malfunctions. Delaying repairs can result in more extensive damage and significantly higher repair costs down the line. Therefore, it is crucial to diagnose and address the rough idle promptly to maintain the optimal performance and longevity of your S2000, ensuring a safe and enjoyable driving experience.

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