1999 Mitsubishi Mirage Has Rough Idle

Diagnosing Causes of Rough Idle in Your 1999 Mitsubishi Mirage 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 1999 Mitsubishi Mirage 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 1999 Mitsubishi Mirage 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.

Customers with drum brake systems often specify they have lost braking power, or that the vehicle's brakes are making noise. This is because brake drums do not dissipate heat very well, so the heat from hard braking will cause stress fractures. These fractures make can make noise on the brake shoes as the drum revolves around the shoes. Lastly, the brake shoes may not be problematic, but may cause a grinding noise while stopping. This would indicate the shoes have no braking material left, and the brake shoes must be changed before the vehicle can be safely driven.

Learn more about brake shoe symptoms

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 1999 Mitsubishi Mirage?

To effectively diagnose a rough idle in your 1999 Mitsubishi Mirage, start with a systematic approach that prioritizes simpler checks before moving on to more complex diagnostics. Begin by inspecting for vacuum leaks, as these can significantly impact engine performance; look for any cracks or disconnections in the vacuum hoses. Next, examine the spark plugs for wear or fouling, as faulty plugs can lead to misfires and rough idling. A clean air filter is also crucial, so check its condition and replace it if it appears dirty or clogged, as this can disrupt the air-fuel mixture. After these initial checks, test the fuel pressure to ensure it meets the manufacturer's specifications, which is vital for proper fuel delivery. The idle air control valve should also be inspected; cleaning or replacing it can resolve issues related to idle stability. Additionally, a thorough cleaning of the throttle body can eliminate carbon buildup that may affect idle quality. Don’t forget to scan for any error codes using an OBD-II scanner, as these can provide insights into underlying issues. Finally, ensure that the coolant level is adequate, as low levels can adversely affect engine performance. By following this structured diagnostic approach, you can effectively identify and address the causes of a rough idle in your vehicle.

What are the common causes of a rough idle in a 1999 Mitsubishi Mirage?

When dealing with a rough idle in your 1999 Mitsubishi Mirage, 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 air filter can significantly restrict airflow to the engine, leading to performance issues. Additionally, inspect the spark plugs, as worn or faulty plugs can cause misfiring, which directly affects engine smoothness. Another critical aspect to examine is the vacuum system for any leaks, as these can disrupt the air-fuel mixture and result in an unstable idle. Fuel system components, including the fuel filter and fuel pump, should also be assessed, as blockages or malfunctions here can hinder engine performance. Furthermore, the Idle Air Control Valve (IACV) plays a vital role in maintaining the correct idle speed, and any faults in this component can lead to rough idling. Lastly, don’t overlook the ignition system; issues with ignition coils or the distributor can also contribute to a rough idle. By systematically checking these areas, you can effectively troubleshoot and potentially resolve the rough idle issue in your vehicle.

How urgent is it to address the rough idle in a 1999 Mitsubishi Mirage?

Addressing a rough idle in your 1999 Mitsubishi Mirage should be treated with a sense of urgency, as neglecting this symptom can lead to a cascade of more serious problems. A rough idle often indicates underlying issues such as dirty fuel injectors, a clogged air filter, or malfunctioning sensors, which, if left unresolved, can escalate into significant engine damage. Moreover, a rough idle can adversely affect your vehicle's performance and fuel efficiency, leading to increased operational costs. If you notice additional symptoms like stalling or misfiring, it becomes even more critical to act quickly, as these can signal imminent engine failure. Regular maintenance and prompt repairs not only enhance your vehicle's longevity but also help you avoid costly repairs in the future. Therefore, while it may not seem like an immediate emergency, addressing a rough idle promptly is essential for maintaining the health and performance of your Mitsubishi Mirage.

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1999 Mitsubishi Mirage Rough Idle: Causes & Repair Costs