6 Signs Your GMC Needs New Spark Plugs

Sluggish Acceleration 

A misfire is when a fouled or failing spark plug misses a beat and doesn’t ignite the fuel-air mixture when it’s supposed to. In that moment, the engine loses a fraction of its ordinary power. The worse the misfiring gets, the weaker your engine and acceleration will become. 

Coughing, Shaking Engine

Spark plugs can misfire for many different reasons. The spark might be weakened by a faulty ignition coil or battery. A clogged air filter or catalytic converter could be restricting the airflow, throwing off the fuel-air mixture, and leading to sooty residue on the spark plugs. 

Most commonly, a misfiring spark plug is simply worn out. Whatever the reason, misfiring will cause your engine to cough and sputter, showing clear signs of struggle, and your truck or SUV will shudder and vibrate. 

Rough Idling and Stalls

Weakening spark plugs cause misfires more when the engine is strained. This happens at higher speeds, when towing or hauling heavy loads, and also when idling. With bad plugs, your engine will roughen and vibrate more when you pause at stop lights or in traffic. Your truck or SUV might also suddenly stall.

Slower Engine Starts

Even with a good starter, reliable engine starts require healthy spark plugs as well. If any of your plugs are weakened by carbon deposits or age, the engine may become hesitant to turn over in the morning. 

Falling Fuel Efficiency

Cylinders with misfiring spark plugs are no longer burning fuel as effectively. This means a portion of the fuel is wasted, reducing your vehicle’s overall gas mileage, and you’ll notice your fuel gauge declining more rapidly than usual. 

Black Smoke Behind You

As bad spark plugs fail to ignite all the fuel, the unburned gas collects inside the combustion chambers. This fouls the spark plugs, worsening the problem. The excess fuel may also escape into the exhaust pipes, wherein it can partially ignite, turning to smoke that pours out of the tailpipe.

Have Your Spark Plugs Checked at Your GMC Dealership

If you’re experiencing any of these symptoms, have your spark plugs inspected immediately. It’s best to have your engine tuned and your spark plugs checked at least once a year. This allows us to identify problems early on and replace worn-out plugs before they cause harm to the vehicle’s engine or catalytic converter.

Visit Marquardt of Barrington GMC in Barrington, IL, today to have your spark plugs cleaned or replaced. We’ve been keeping the engines of our customers’ trucks and SUVs running smoothly and powerfully for over 75 years. 

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