2015 Cadillac ATS Has Rough Idle

Common Causes of Rough Idling in Your 2015 Cadillac ATS 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 2015 Cadillac ATS 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 2015 Cadillac ATS 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 2015 Cadillac ATS?

To effectively diagnose a rough idle in your 2015 Cadillac ATS, start with a systematic approach that prioritizes simpler checks before moving on to more complex diagnostics. Begin by using an OBD-II scanner to check for any error codes, as these can provide immediate insights into potential issues. Next, inspect the spark plugs for wear or fouling, as they play a crucial role in engine performance. A clean air filter is essential for optimal airflow, so ensure it is free from dirt and debris. Don’t overlook the vacuum hoses; any cracks or disconnections can lead to performance problems. Additionally, examine the fuel system, focusing on the fuel filter and injectors, as blockages here can significantly affect idling. The mass airflow sensor is another critical component; if it’s malfunctioning, it can disrupt the air-fuel mixture, leading to rough idling. Finally, inspect and clean the throttle body, as a buildup of dirt can hinder engine performance. By following this structured diagnostic approach, you can identify and resolve the underlying causes of a rough idle in your Cadillac ATS.

What are the common causes of a rough idle in a 2015 Cadillac ATS?

When diagnosing a rough idle in your 2015 Cadillac ATS, it's crucial to consider several common problems that could be at play. One of the primary culprits is a dirty or clogged air filter, which can significantly restrict airflow to the engine, leading to an uneven idle. Additionally, faulty spark plugs are notorious for causing misfires; if they are worn out, they can disrupt the combustion process and result in a rough idle. Another potential issue is vacuum leaks, which can disturb the delicate air-fuel mixture necessary for smooth engine operation. Fuel system problems, such as clogged fuel filters or injectors, can also hinder performance and contribute to rough idling. Furthermore, a malfunctioning mass airflow sensor can throw off the air-fuel balance, exacerbating the issue. Lastly, don't overlook the Exhaust Gas Recirculation (EGR) valve; if it's faulty, it can interfere with combustion and lead to a rough idle. By addressing these common problems, you can restore your Cadillac ATS to optimal performance and enjoy a smoother driving experience.

How urgent is it to address the rough idle in a 2015 Cadillac ATS?

Addressing a rough idle in your 2015 Cadillac ATS is not just a matter of comfort; it’s crucial for the vehicle's overall health and performance. A rough idle can indicate underlying issues such as fuel system malfunctions, ignition problems, or sensor failures, which, if left unchecked, may lead to more severe engine damage. Ignoring this symptom can result in decreased fuel efficiency and poor vehicle performance, ultimately costing you more in repairs down the line. Moreover, a rough idle can escalate into serious safety concerns, particularly if it affects engine responsiveness. For DIY enthusiasts, it’s essential to prioritize this issue and conduct a thorough inspection of the engine components. Regular maintenance and prompt attention to symptoms like a rough idle can save you from costly repairs and ensure your Cadillac ATS runs smoothly for years to come.

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2015 Cadillac ATS Rough Idle: Causes & Repairs | RepairPal