Faulty Spark Plugs and Auto Rough Idle

Have you ever felt like your car’s engine was shaking or stuttering when just idling?  This is known as Rough Idle. Potential causes of a rough idle include clogged fuel injectors, vacuum leaks,  malfunctioning idle control valves, and Faulty Spark Plugs. However, this blog focuses on the small spark plugs because of their key role in the overall performance of an engine. They ignite the air-fuel mixture inside the combustion chamber to power the vehicle. When spark plugs are worn out or damaged, they struggle to provide a consistent spark, causing the engine to misfire during idle, resulting in a rough and shaky idle. 

Diagnosing Faulty Spark Plugs

Determining whether faulty spark plugs are the root cause of a rough idle requires a systematic approach. Here’s a step-by-step guide to diagnosing spark plug issues:

• Visual Inspection: Start by visually inspecting the spark plugs. Look for signs of wear, such as eroded electrodes or excessive carbon buildup. If any plugs appear damaged or worn, it’s time for a replacement.
• Spark Plug Test: Use a spark plug tester to check each plug for spark. A weak or absent spark indicates a faulty plug and warrants replacement.
• Compression Test: Check the engine cylinders’ pressure by using a compression test. Since low compression can cause a rough idle, it may rule out faulty spark plugs.
• Computer Diagnostic: Utilize a computer diagnostic tool to scan the vehicle’s onboard computer system for error codes related to the ignition system.

Taking the time to diagnose the issue accurately will save you from unnecessary expenses and ensure that you address the root cause of the rough idle.

Steps to Replace Spark Plugs 

Once you’ve determined that faulty spark plugs are causing the rough idle, it’s time to replace them. If you want to tackle this task yourself, here’s a step-by-step guide.

• Gather the necessary tools: You’ll need a socket wrench, a spark plug socket, a spark plug gap gauge, and a torque wrench.
• Locate the spark plugs: Refer to your vehicle’s manual to find the location of the spark plugs. Most engines have them situated in a row along the top or side of the engine block.
• Remove the spark plug wires: Carefully detach them from the spark plugs, ensuring you don’t pull on the wires themselves.
• Remove the old spark plugs: Using a spark plug socket and a socket wrench, loosen and remove the old spark plugs one by one. Check the gap of the new spark plugs using a spark plug gap gauge and adjust if necessary.
• Install the new spark plugs: Insert them into the spark plug socket and carefully thread them into the engine block by hand. Once snug, use a torque wrench to tighten them to the manufacturer’s specifications.
• Reconnect the spark plug wires: Attach them back onto the corresponding spark plugs, ensuring they are securely connected.

Replacing your spark plugs resolves the rough idle issue and improves engine performance, fuel efficiency, and overall drivability.

Schedule Spark Plugs Service

Not everyone has the know-how, time, or desire to indulge in even minor car repairs.

That’s why the  ASI-Certified Technicians at Wentworth Automotive have you covered. They will gladly discuss your Tune-up and Spark Plugs replacement needs. Visit them online or call (858) 541-1044 to schedule your service.