Jeep Grand Cherokee Has Rough Idle

Troubleshooting Causes of Rough Idle in Your Jeep Grand Cherokee and How to Resolve Them

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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 Jeep Grand Cherokee 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 Jeep Grand Cherokee 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.

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.

Troubleshooting Rough Idle in a Jeep Grand Cherokee

When troubleshooting rough idle issues in your Jeep Grand Cherokee, it's essential to adopt a methodical diagnostic approach. Begin by using an OBD scanner to check for any trouble codes, as this can quickly highlight specific problems, particularly with the idle air control valve, which is a common culprit. Next, inspect the air intake system, including the MAF or MAP sensor, to ensure that air is being metered correctly into the engine. Pay attention to the air-to-fuel ratio, aiming for the ideal 14.7:1, as deviations can lead to rough idling. Additionally, assess the condition of the motor mounts; any signs of fluid leaks or excessive movement when revving the engine may indicate a need for replacement. If these initial checks do not resolve the issue, consider examining the fuel system and transmission for underlying problems. By systematically addressing these areas, you can effectively diagnose and remedy rough idle conditions, restoring your vehicle's performance.

What Are the Common Causes of Rough Idle in a Jeep Grand Cherokee?

When dealing with a rough idle in your Jeep Grand Cherokee, it's essential to understand the common problems that could be causing this issue. One of the primary suspects is a vacuum leak, which can disrupt the air-fuel mixture and lead to an unstable engine performance. Inspecting hoses and connections for any signs of wear or damage can help you identify and fix this problem. Additionally, worn or faulty spark plugs can contribute to rough idling by failing to ignite the fuel properly, so checking their condition and replacing them if necessary is a good step. Lastly, issues with the ignition coil can also lead to misfires and rough idling; testing the coil's functionality can help determine if it needs replacement. By systematically checking these components, you can effectively troubleshoot and potentially resolve the rough idle issue in your Jeep Grand Cherokee.

Why is a Jeep Grand Cherokee Idling Rough and What Should You Do?

When your Jeep Grand Cherokee is idling rough, it’s crucial to address the issue promptly to avoid more severe problems down the line. Ignoring symptoms like misfiring, which can stem from inadequate air, fuel, or spark, may lead to engine damage or decreased performance. Additionally, a vacuum leak can disrupt the air-fuel mixture, causing erratic idling and potentially straining the engine. Faulty spark plugs and ignition coils can exacerbate these issues, leading to poor fuel efficiency and increased emissions. Moreover, problems with the idle air control valve can result in stalling or fluctuating RPMs, which not only affects drivability but can also pose safety risks on the road. By diagnosing and resolving these issues early, you can prevent costly repairs and ensure your Jeep operates smoothly and safely. Therefore, if you notice your vehicle idling roughly, it’s advisable to take action immediately, whether through DIY troubleshooting or consulting a qualified technician.

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