Spark Plug Conditions


Symptoms: Has a brown to gray color tint with a small amount of electrode wear.

Recommendation: Replace when signs of wear appear or at the designated mileage. 

Ash Deposits
Symptoms: Light brown deposits caked on the electrode. Caused by oil/fuel additives. Excessive amounts may cause the spark to be absorbed resulting in misfiring and hesitation during acceleration.
Recommendation: If the deposits build up over a short amount of time or mileage, try changing to a different gasoline manufacturer. If the problem persists install new valve guide seals.

Carbon Deposits
Symptoms: Powdery deposits are signs of a rich mixture or a faulty ignition. This can lead to misfiring, acceleration hesitation, and hard starting.
Recommendations: Check the temperature range of the spark plug and make sure it is the correct plug for your model. Also check for a clogged air filter and inspect your fuel system. If the problem persists have your ECM inspected.


Symptoms: The ceramic insulators might be cracked or chipped and/or electrodes burned away due to an improper gap setting. This can lead to engine damage.
Recommendations: Make sure the octane level in your gas is at the minimum level recommended by BMW. Also take care when gapping the plugs as that some of them are non-adjustable. If your BMW is equipped with a stick shift transmission, avoid excessive low RPMs or lugging.

Gap Bridging

Symptoms: Carbon build up between the electrodes. A heavy accumulation builds up and causes a bridge to form resulting in a dead plug.
Recommendation: Thoroughly clean the plug or replace it.

High Speed Glazing

Symptoms: Ceramic insulator has a glazed yellow appearance to it. This results from combustions chamber temperatures rising quickly during hard accelerations. During these extreme temperatures the carbon deposits are melted onto the plug forming a conductive layer causing misfires at high RPMs.
Recommendations: Replace plugs. If your daily driving habits include considerable amounts of high RPMs consider using a colder plug.

Too Hot

Symptoms: Fractured, white ceramic insulator, worn electrode, and lack of carbon deposits. Plug life is decreased.
Recommendations: Check the temperature range of the spark plug, over-advanced timing, lean fuel mixture, vacuum leaks around the intake manifold, possible stuck valves, and lack of proper engine cooling.

Physical Damage

Symptoms: Objects in the combustion chamber or piston slap due to incorrect plugs.
Recommendations: Inspect pistons/combustion chamber for objects and replace pistons if damaged. Insure correct plug has been installed with spark plugs recommended by BMW.

Oil Deposits

Symptoms: Oil buildup or sludge. This is cause by worn valve guides and/or worn piston rings resulting in misfires, hesitations, and hard starts.
Recommendations: Repair defective item(s) and install new plugs.


Symptoms: Electrodes are melted. The ceramic Insulators are white, but it could be dirty from debris or misfiring. This can lead to engine damage.
Recommendations: Check the temperature range of the spark plug, over-advanced timing, fuel mixture too lean, improper engine cooling.


Symptoms: Worn electrodes with light deposits on the tip. Normal color and deposits. Can cause hard starts in cold/wet climate conditions and poor gas mileage.
Recommendations: Plugs are old and need to be replace on a regularly basis with plugs recommended by BMW.


Vines Automotive