1998 INFINITI QX4 Has Rough Idle

Troubleshooting Causes of Rough Idle in Your 1998 INFINITI QX4 and How to Restore Smooth Performance

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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 1998 INFINITI QX4 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 1998 INFINITI QX4 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 1998 INFINITI QX4?

To effectively diagnose a rough idle in your 1998 INFINITI QX4, 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 affect engine performance. Next, examine the spark plugs; worn or fouled plugs can lead to misfires and rough idling. A clean air filter is essential for optimal airflow, so check its condition and replace it if necessary. Following this, assess the fuel system by testing the fuel pressure and inspecting the injectors to ensure they are delivering fuel properly. Utilizing an OBD-II scanner can help identify any error codes that may point to sensor malfunctions or other issues. Don’t overlook the idle air control valve, as dirt or carbon buildup can disrupt its function, leading to an unstable idle. Cleaning the throttle body is also crucial, as carbon deposits can hinder airflow. Finally, verify the operation of the engine coolant temperature sensor, since its readings can influence the engine's idle speed. By following this structured diagnostic approach, you can effectively pinpoint and resolve the cause of a rough idle in your vehicle.

What are the common causes of a rough idle in a 1998 INFINITI QX4?

When addressing a rough idle in a 1998 INFINITI QX4, it's important to consider several common problems that may be affecting engine performance. A dirty or clogged air filter can significantly limit airflow, leading to an uneven idle. Additionally, worn or faulty spark plugs can cause misfires, which contribute to the roughness. Vacuum leaks are another frequent issue, as they can disrupt the air-fuel mixture necessary for smooth operation. Problems within the fuel system, such as a clogged fuel filter or a malfunctioning fuel pump, can further impact engine performance and exacerbate idle issues. The Idle Air Control Valve (IACV) is also a critical component; if it malfunctions, it can lead to irregular idle speeds. Lastly, ignition system problems, including faulty ignition coils or distributors, can manifest as a rough idle as well. By diagnosing these common issues, you can effectively restore your QX4's smooth engine operation.

How urgent is it to address the rough idle in my 1998 INFINITI QX4?

Addressing a rough idle in your 1998 INFINITI QX4 is not just a matter of convenience; it is crucial for maintaining the overall health and performance of your vehicle. Ignoring this symptom can lead to serious engine problems, such as misfiring cylinders or fuel system malfunctions, which may result in costly repairs down the line. Additionally, a rough idle can significantly decrease your vehicle's fuel efficiency, leading to higher fuel costs and an increased environmental impact due to elevated emissions. This not only affects your wallet but could also cause your vehicle to fail emissions tests, putting you at risk of legal penalties. Furthermore, the discomfort caused by vibrations and inconsistent engine performance can detract from your driving experience, making it less enjoyable and potentially distracting. Therefore, it is imperative to address a rough idle promptly to avoid these negative consequences and ensure your INFINITI QX4 operates smoothly and efficiently.

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