2018 BMW 640i XDrive Gran Turismo Has Rough Idle

Resolve Rough Idle in 2018 BMW 640i xDrive Gran Turismo for a Smoother Ride

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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 2018 BMW 640i xDrive Gran Turismo 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 2018 BMW 640i xDrive Gran Turismo 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 initial diagnostic steps to take for a rough idle in a 2018 BMW 640i xDrive Gran Turismo?

When faced with a rough idle in your 2018 BMW 640i xDrive Gran Turismo, it's essential to adopt a systematic diagnostic approach to identify the root cause effectively. Start by checking for fault codes using a diagnostic scanner, as these codes can reveal specific issues within the engine management system. Next, inspect the spark plugs for wear or fouling, as they play a crucial role in engine performance. Following this, evaluate the air intake system for any leaks or blockages that could disrupt the air-fuel mixture. Don’t overlook the vacuum hoses; any cracks or leaks here can significantly impact engine operation. Additionally, test the mass airflow sensor to ensure it is functioning correctly, as inaccuracies can lead to improper air intake measurements. Finally, assess the fuel system, including the fuel filter and injectors, to rule out any clogs or malfunctions. By methodically working through these steps, you can effectively diagnose and address the rough idle issue, ensuring your BMW runs smoothly.

What are the common problems that could cause a rough idle in a 2018 BMW 640i xDrive Gran Turismo?

When dealing with a rough idle in your 2018 BMW 640i xDrive Gran Turismo, it's essential to consider several common problems that could be affecting your vehicle's performance. One of the primary culprits is a dirty or faulty mass airflow sensor, which can disrupt the delicate balance of the air-fuel mixture, leading to an unstable idle. Additionally, vacuum leaks can create an improper air-fuel ratio, further exacerbating the rough idle issue. It's also crucial to inspect the spark plugs and ignition coils, as worn components can cause misfires that manifest as rough idling. A clogged fuel filter may restrict fuel flow, impacting engine performance, while issues with the idle control valve can disrupt the engine's idle speed. Lastly, a dirty throttle body can hinder airflow, contributing to the rough idle experience. By systematically checking these components, you can identify and address the underlying issues, ensuring smoother operation of your BMW.

How urgent is it to address the rough idle in a 2018 BMW 640i xDrive Gran Turismo?

Addressing a rough idle in your 2018 BMW 640i xDrive Gran Turismo should be a priority, as neglecting this issue can lead to more severe engine problems and decreased performance. A rough idle often indicates underlying issues, such as fuel delivery problems, ignition system failures, or vacuum leaks, which can worsen over time if not promptly diagnosed and repaired. Ignoring these symptoms not only risks further damage to the engine but can also result in decreased fuel efficiency, leading to higher operating costs. For DIY enthusiasts, it’s crucial to recognize that while some minor adjustments can be made at home, a thorough diagnostic by a professional mechanic is often necessary to accurately pinpoint the root cause of the rough idle. This proactive approach not only helps maintain the vehicle's performance but also prevents potentially costly repairs in the future, ensuring that your BMW continues to run smoothly and efficiently.

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