2015 BMW 328i XDrive Has Rough Idle

Diagnosing Causes of Rough Idle in Your 2015 BMW 328i xDrive and Solutions for a Smoother Ride

Find Repair Location
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 2015 BMW 328i xDrive has rough idle are a vacuum leak, an issue with the spark plugs, or a problem with the ignition coil.
  • Spark Plugs: A worn or fouled spark plug can cause misfires, rough idling, and decreased fuel efficiency due to incomplete combustion.
  • 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 BMW 328i xDrive 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 BMW 328i xDrive?

To effectively diagnose a rough idle in your 2015 BMW 328i xDrive, start with a systematic approach that prioritizes simpler checks before delving into more complex issues. Begin by inspecting the Mass Airflow (MAF) sensor, as a malfunctioning MAF can significantly impact engine performance; temporarily unplugging it may provide immediate insight into whether it’s the source of the problem. Next, examine the idle control valve, which plays a crucial role in maintaining a stable idle speed; cleaning or replacing this component can often resolve rough idling. Additionally, ensure that you are using high-quality fuel and that the intake system is free from dirt and contaminants, as these factors can contribute to engine irregularities. Pay attention to temperature variations, especially if the rough idle occurs primarily during cold starts, as this can indicate a temperature-related issue. If these initial steps do not resolve the problem, it may be wise to consult a BMW specialist for a thorough diagnosis, ensuring that any underlying issues are addressed effectively. By following this structured diagnostic approach, you can identify and rectify the rough idle in your BMW with greater confidence.

What are the common problems that could cause a rough idle in a 2015 BMW 328i xDrive?

When dealing with a rough idle in a 2015 BMW 328i xDrive, it's essential to consider several common problems that could be affecting your vehicle's performance. One of the primary culprits is faulty spark plugs, which can lead to misfires and an unsteady idle. If the spark plugs are worn or damaged, replacing them can often resolve the issue. Another potential problem is the eccentric shaft sensor; if this sensor is failing, it may cause rough idling, particularly at startup, due to oil leakage. Additionally, the Mass Airflow Sensor (MAF) plays a crucial role in regulating air intake, and disconnecting it may temporarily smooth out the idle, indicating a possible malfunction. Other factors, such as poor acceleration, low fuel efficiency, and vibrations while idling, can also contribute to a rough idle. For DIY enthusiasts, it's advisable to conduct a thorough inspection of these components and consider regular maintenance to ensure optimal performance and longevity of your BMW 328i xDrive.

How urgent is it to address the rough idle in my 2015 BMW 328i xDrive?

Addressing a rough idle in your 2015 BMW 328i xDrive should not be overlooked, as it can signal various underlying issues that may escalate if neglected. The urgency of this problem lies in its potential to affect engine performance and fuel efficiency, leading to more severe complications down the line. For DIY enthusiasts, it's crucial to understand that rough idling can stem from factors such as vacuum leaks, unmetered air entering the engine, or a malfunctioning idle control valve. Ignoring these symptoms can result in costly repairs and even engine damage, making it essential to diagnose and resolve the issue promptly. While it may not pose an immediate safety risk, the long-term implications of a rough idle can significantly impact your vehicle's reliability and performance. Regular maintenance and timely intervention are key to ensuring your BMW remains in optimal condition, so if you notice a rough idle, consider investigating the root cause and addressing it as soon as possible to avoid further complications.

You’ve got options with RepairPal

Whether you need a more accurate auto repair estimate or help finding a reputable shop in your area, we’ve got you covered.

2015 BMW 328i xDrive Rough Idle Causes & Repairs | RepairPal