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Jun 23, 2024 · A spark plug running lean can show symptoms such as a lack of power, slow acceleration, overheating of the engine, engine misfires, or a surge in RPM. These signs generally indicate insufficient fuel in the air-fuel mixture.
Jan 18, 2023 · The spark plug will overheat and cause an anomalous ignition firing (pre-ignition), which can result in the melting of the spark plug electrodes as well as piston seizure and erosion. When the heat range is too low, it can be exceedingly harmful to your car’s engine.
- Normal Condition. An engine’s condition can be judged by the appearance of the spark plug’s firing end. If the firing end of a spark plug is brown or light gray, the condition can be judged to be good and the spark plug is functioning optimally.
- Dry and Wet Fouling. Although there are many different cases, if the insulation resistance between the center electrode and the shell is over 10 ohms, the engine can be started normally.
- Overheating. When a spark plug overheats, deposits that have accumulated on the insulator tip melt and give the insulator tip a glazed or glossy appearance.
- Deposits. The accumulation of deposits on the firing end is influenced by oil leakage, fuel quality and the engine’s operating duration.
- Normal
- Deposits
- Wet and Dry Fouling
- Lead Fouling
- Breakage
- Melting
- Lead Erosion
- Erosion, Corrosion & Oxidation
- Overheating
Appearance: A light tan/gray or brownish color, along with very little electrode erosion, indicates optimal operation conditions, including a healthy engine and correct spark plug heat range.
Appearance & Symptoms: The electrodes—center and ground—are covered in an ashy coating. As a result of this masking of the electrodes, your engine may experience a misfire. This build-up of combustion deposits can eventually (but not usually) fill in the space between the two electrodes. Possible Causes: Oil leaks, poor fuel quality.
Appearance & Symptoms: Dry fouling (top) appears as sooty, black build-up. Wet fouling (bottom) has a wet, sometimes oily appearance. Both conditions can create poor starting and misfiring. Possible Causes: Depending on whether the spark plug is coated in oil or fuel, wet fouling can be symptomatic of a compromised head gasket, poor control from yo...
Appearance & Symptoms: Lead fouling can only occur in applications that use leaded gasoline, such as racing engines. Lead fouling generally shows up as yellowish brown deposits on the spark plug’s insulator nose. Lead fouling can cause your engine to misfire only at high-rpm and under hard acceleration. Possible Causes: This condition commonly occu...
Appearance & Symptoms: The insulator around the center electrode may be broken (see left) or the ground electrode may be bent. Again, you will likely experience misfire and some power loss under these conditions. Possible Causes: If the insulator is broken, it may be the result of sudden thermal expansion or thermal shock caused by extreme temperat...
Appearance & Symptoms: In this case, the center or ground electrode is melted or scorched, and your engine may be experiencing some power loss. Possible Causes: According to NGK, melting often results from loose installation, which prevents the plug from properly transferring heat from its tip. But melting may also indicate unusual heat or hot spot...
Appearance & Symptoms: The tip of the ground electrode looks chipped and its surface may be thinned. Possible Causes: Another condition unique to leaded gasoline, this condition is caused by lead compounds that react chemically with the electrodes at high temperatures. This makes the electrode material (nickel alloy) weak and brittle. This is cause...
Appearance & Symptoms: A plug with a combination of erosion, corrosion, and oxidation will have pitted and rough electrodes and may even have a green cast if the oxidation is heavy. These conditions can result in increased, improper spark plug gap and yield poorer performance. Possible Causes: Typically, these conditions occur over time as lead in ...
Appearance & Symptoms: The insulator will have a glazed white appearance and may have small black deposits. There may also be abnormal electrode wear, and you will likely notice a loss of power at high speeds or under high engine load. Possible Causes: Overheating may occur from over-advanced ignition timing, poor cooling system efficiency, lean ai...
If an engine is too rich, the spark plugs will look black or glossy black, depending on how rich the engine is. In contrast, the spark plugs will be greyish-white if the engine runs lean. How do you read the timing mark on a spark plug?
Jul 10, 2020 · Spark plug heat range is the relative temperature of the spark plug's core nose. Critical factors involved in choosing the correct spark plug heat range include: 1. Air/Fuel Mixture:...
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If you are experiencing engine problems, taking a look at your spark plugs is a good place to start. When reading spark plugs, you will likely find one of the following conditions: Normal. Carbon fouled. Oil deposits. Wet. Burned. Worn electrodes. Broken electrodes.
