2014 BMW 335i Has Rough Idle

Troubleshooting Causes of Rough Idle in Your 2014 BMW 335i and How to Restore Smooth Performance

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Reviewed by

Aisha

Written by RepairPal Car Genius

Updated January 14, 2025

21% chance it's the

Spark Plugs

15% chance it's the

Ignition Coil

64% chance it's

Something else

The most common reasons a 2014 BMW 335i 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.

What are the best BMW repair shops?

RepairPal Certified shops can diagnose and repair your 2014 BMW 335i engine and performance issues. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.

How much does it cost to fix a 2014 BMW 335i 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:

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.
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.
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.
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 common causes of a rough idle in a 2014 BMW 335i?

When dealing with a rough idle in a 2014 BMW 335i, 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 unstable idle. Additionally, issues with the Idle Control Valve (ICV) can disrupt the regulation of idle speed, often due to dirt or malfunctioning components. Another significant factor to investigate is the presence of a vacuum leak or a failed Positive Crankcase Ventilation (PCV) valve, both of which can create imbalances in the air-fuel mixture, resulting in rough idling. Clogged fuel injectors are also a common issue, as they can hinder the engine's ability to maintain a proper air-fuel ratio. Furthermore, problems related to the air-fuel mixture, such as malfunctioning EGR valves or low engine compression, can exacerbate idle issues. Lastly, misfires caused by bad spark plugs or ignition coils, though less frequent, can also contribute to a rough idle. Addressing these factors promptly is crucial for maintaining your BMW's performance and ensuring a smoother driving experience.

How urgent is it to address the rough idle in my 2014 BMW 335i?

Addressing a rough idle in your 2014 BMW 335i is not just a matter of comfort; it is crucial for the vehicle's overall performance and safety. A rough idle can indicate serious underlying issues such as faulty spark plugs, a clogged fuel filter, or ignition system problems. Ignoring these symptoms can lead to decreased fuel efficiency and may cause further damage to the engine, potentially resulting in costly repairs. Moreover, a rough idle can compromise your vehicle's safety, as it may lead to unpredictable engine behavior while driving. Therefore, it is essential to prioritize this issue and seek a professional diagnosis promptly. By addressing the rough idle early, you can maintain the reliability and longevity of your BMW, ensuring a smoother and safer driving experience.

Related 2014 BMW 335i Problems

Read about related problems experienced by other BMW 335i drivers like you.

BMW 335i hard starting issue due to high pressure fuel pump and fuel rail pressure sensor replacement needed

Some BMW 335i owners report experiencing hard starting issues related to the high-pressure fuel pump (HPFP) and fuel rail pressure sensor, which can manifest as long cranks during startup and the illumination of the malfunction engine light while driving. These problems may require diagnosis by a certified BMW mechanic to determine if the HPFP is the underlying cause. If low fuel pressure is detected and the pump isn't priming, owners might need to replace the entire pump assembly. In certain cases, issues like a blocked pump can be repaired, but replacement of both the high-pressure rail sensor and the updated low-pressure sensor may also be necessary. A failing HPFP can lead to unexpected stalling, particularly during idle or low-speed driving, and can result in reduced engine power, rough idling, and even complete engine failure. Therefore, accurate diagnosis and timely replacement of components are essential for resolving these serious issues.

2 model years affected

Avg Mileage: 165,083

11 others reported problem

4 comments

Jaguar XKR rough idling issue with trouble codes indicating random multiple misfire in one bank

Some Jaguar XKR owners report experiencing rough idling issues accompanied by trouble codes indicating random multiple misfires, such as P0300, P0302, and P0304, which are linked to specific cylinders like cylinder 2 and cylinder 4. These owners often identify potential causes including vacuum leaks, spark plug problems, or ignition coil failures. Additionally, some report symptoms of fuel starvation, prompting checks of fuel pressures for accurate diagnosis. Issues with the supercharger bypass valve have also been noted as a contributing factor to rough idling. Furthermore, maintaining the correct air-to-fuel ratio is crucial, as any discrepancies can exacerbate misfires and idling issues. To resolve these problems, owners may need to reset fault codes, check fuel pressure, inspect the supercharger bypass valve, and ensure optimal air-to-fuel ratios.

1 model year affected

See More 2014 BMW 335i Problems

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