Difference between revisions of "Misfire"
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| + | ===Steady Misfire=== | ||
| − | + | In the case of a steady misfire, isolating the misfiring cylinder is the first step in diagnosing the problem. The old-fashioned method for finding a weak cylinder is to temporarily disconnect each of the spark plug wires, one at a time, while the engine is idling. When there's no change in the idle speed, then you have pinpointed the weak cylinder. | |
| + | A power balance test will tell you the same thing, but it requires some hookups and an engine analyzer. A power balance test is preferable to pulling plug wires, because it keeps you away from the voltage and prevents the voltage from causing any damage to the electronics in the ignition system. | ||
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| + | '''Items that can cause a misfire:''' | ||
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| + | ===Spark Plugs=== | ||
[[Spark plugs]] | [[Spark plugs]] | ||
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| + | ===Coil Packs=== | ||
[[Coil packs]] | [[Coil packs]] | ||
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| + | ===Idle Air Control Valve=== | ||
[[Idle Air Control Valve]] (IACV) | [[Idle Air Control Valve]] (IACV) | ||
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| + | ===Lambda Sensor=== | ||
[[Lambda sensor]] | [[Lambda sensor]] | ||
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| + | ===Head Gasket Failure=== | ||
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| + | A spark plug that shows heavy whitish to brown deposits may indicate a coolant leak either past the head gasket or through a crack in the combustion chamber. This type of problem will only get worse and may soon lead to even greater problems if the leak isn't fixed. Coolant makes a lousy lubricant and can cause ring, cylinder and bearing damage if it gets into a cylinder or the crankcase. | ||
[[Head gasket failure]] | [[Head gasket failure]] | ||
Revision as of 08:21, 6 May 2007
Misfire
Steady Misfire
In the case of a steady misfire, isolating the misfiring cylinder is the first step in diagnosing the problem. The old-fashioned method for finding a weak cylinder is to temporarily disconnect each of the spark plug wires, one at a time, while the engine is idling. When there's no change in the idle speed, then you have pinpointed the weak cylinder.
A power balance test will tell you the same thing, but it requires some hookups and an engine analyzer. A power balance test is preferable to pulling plug wires, because it keeps you away from the voltage and prevents the voltage from causing any damage to the electronics in the ignition system.
Items that can cause a misfire:
Spark Plugs
Coil Packs
Idle Air Control Valve
Idle Air Control Valve (IACV)
Lambda Sensor
Head Gasket Failure
A spark plug that shows heavy whitish to brown deposits may indicate a coolant leak either past the head gasket or through a crack in the combustion chamber. This type of problem will only get worse and may soon lead to even greater problems if the leak isn't fixed. Coolant makes a lousy lubricant and can cause ring, cylinder and bearing damage if it gets into a cylinder or the crankcase.