Fouled Spark Plug Chart: What Could Cause Your Vehicle to Perform Improperly

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Fouled Spark Plug Chart

Need to know how to read fouled spark plug chart? Knowing the sign of damaged or fouled spark plugs is important for every car owner, considering if these components go wrong, there are plenty of problems that will follow such as difficulty in starting the engine, engine misfires, slow acceleration, and reduced gas mileage.

Examining the spark plugs of your vehicle can be included as a part of its routine maintenance or whenever you reckon there’s something wrong with the engine. You need to remove the spark plug first and observe it to look for any damage sign. Examine the spark plug’s end in the cylinder and see if it has the normal appearance of showing grayish-tan or brow deposits on the electrode’s side.

Otherwise, check out the following list below that offer an easier way to understand fouled spark plug chart:

Carbon deposits

Carbon-fouled plug is indicated by dry and black carbon on the insulator tip and electrodes, which might be caused by intense air/fuel mixture, numerous idling, excessive low speed-driving, or dirty air filter. This problem usually requires replacement of damaged spark plugs.


Oil fouled

Oil-fouled plug is symptomized by oily and black deposits on the insulator tip and electrodes. Oil might travel into worn valve guides, aged pistons or cylinders. It’s important to reach mechanic to discover the leakage source. Spark plug replacement may be needed.



Engine flooding—which happens when the engine is started a few times without being fired up—typically causes wet spark plugs. It usually can be resolved by waiting for the spark plugs to dry out or clean them.



Burned spark plugs operating too hot are indicated by white deposits, molten electrodes, or bulge on the insulator tip. These may be caused by improper heat range of spark plugs, engine overheating, improper ignition timing, unsecured spark plug, or lean mixture of air and fuel. It requires replacement of the spark plugs.


Weary electrodes

Next method to how to know if spark plugs are fouled is by checking if they have aged and eroded electrodes. At this point, the plugs need replacement.


Damaged electrodes

Flattened or severed electrode may happen if you install the incorrect spark plugs, such as the ones too long or too short. Refer and follow the manual book to make sure that you install the right spark plug for the vehicle.

If there is indeed a problem with the spark plugs of your vehicle, it usually requires for a replacement or reinstallation. When you use fouled spark plug chart to check the condition of this vehicle part, make sure you inspect each possible symptom thoroughly, one after the other.

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