Spark Plug Tip Tips

Spark plugs wear down over time, but how they wear can tell you a lot about your engine and how it’s performing. Here’s a quick tip guide to spark plug tips!

#1 Normal Wear    

Symptoms: Brown to grayish-tan color and slight electrode wear. Correct heat range for engine and operating conditions.

Recommendation: When new spark plugs are installed, replace with plugs of the same heat range.

#2 Worn

Symptoms: Rounded electrodes with small amounts of deposits on the firing end. Normal color. Causes hard starting in damp or cold weather and poor fuel economy.

Recommendation: Plugs have been left in the engine too long. Replace with new plugs of the same heat range. Follow the recommended maintenance schedule.

#3 Carbon Deposits

Symptoms: Dry, sooty deposits indicate a rich mixture or weak ignition. Causes misfiring, hard starting and hesitation.

Recommendation: Make sure the plug has the correct heat range. Check for a clogged air filter or problem in the fuel system. Also check for other ignition problems.

#4 Ash Deposits

Symptoms: Light brown deposits encrusted on the side or center electrodes or both. Derived from oil and or fuel additives. Excessive amounts may mask the spark, causing misfiring and hesitation during acceleration.

Recommendation: If excessive deposits accumulate over a short period of time (or low mileage), install new valve guide seals to prevent seepage of oil into the combustion chambers. Also try changing gasoline brands.

#5 Oil Deposits

Symptoms: Oily coating caused by poor oil control. Oil is leaning past work valve guides or piston rings into the combustion chamber. Causes hard starting, misfiring and hesitation.

Recommendation: Correct the mechanical condition with necessary repairs and install new plugs.

#6 Gap Bridging

Symptoms: Combustion deposits lodge between the electrodes. Heavy deposits accumulate and bridge the electrode gap. The plug cease to fire, resulting in a dead cylinder.

Recommendation: Locate the faulty plug and remove the deposits from between the electrodes, or replace with a new spark plug of the same heat range.

#7 Too Hot

Symptoms: Blistered, white insulator, eroded electrode and absence of deposits. This results in shorted plug life.

Recommendation: Check for the correct plug heat range, over-advanced ignition timing, lean fuel mixture, intake manifold or vacuum leaks, sticking valve and insufficient engine cooling.

#8 Pre-Ignition

Symptoms: Melted electrodes. Insulators are white but may be dirty due to misfiring or flying debris in the combustion chamber. Can lead to engine damage.

Recommendation: Check for the correct plug heat range, over-advanced timing, lean fuel mixture, insufficient engine cooling or lack of lubrication.

#9 High Speed Glazing

Symptoms: Insulator has yellowish, glazed appearance. Indicates that combustion chamber temperatures have risen suddenly during hard acceleration. Normal deposits melt to form a conductive coating. Causes misfiring at high speeds.

Recommendation: Install new plugs. Consider using a cooler plug if driving habits warrant.

#10 Detonation

Symptoms: Insulators may be cracked or shipped. Improper gap setting techniques can also result in a fractured insulator tip. Can lead to piston damage.

Recommendation: Make sure the fuel anti-knock valves meet engine requirements. Use care when setting the gaps on new plugs. Avoid lugging the engine.

#11 Mechanical Damage

Symptoms: May be caused by a foreign object in the combustion chamber or the piston striking an incorrect reach (too long) plug. Causes a dead cylinder and could result in piston damage.

Recommendation: Repair the mechanical damage. Remove the foreign object from the engine and/or install the correct reach plug.