Difference between revisions of "Misfire"

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===Steady 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.
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In the case of a steady misfire, isolating the misfiring cylinder is the first step in diagnosing the problem.  
  
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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===Loose/disconnected HT Leads===
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Check they are all attached properly! (Cured my misfire anyway....)
  
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===Moisture in Distributor (Dizzy) Cap===
  
'''Items that can cause a misfire:'''
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Unscrew, check for moisture, dry off. 
  
 
===Spark Plugs===
 
===Spark Plugs===
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[[Coil packs]]
 
[[Coil packs]]
  
===Idle Air Control Valve===
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===Throttle Position Sensor===
 
 
[[Idle Air Control Valve]]  (IACV)
 
  
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[[Throttle Position Sensor]]
  
 
===Lambda Sensor===
 
===Lambda Sensor===
  
 
[[Lambda sensor]]
 
[[Lambda sensor]]
 
  
 
===Head Gasket Failure===
 
===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.
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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.
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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]]
  
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===Inlet Manifold Gasket Failure===
  
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The Inlet manifold gasket can fail and allow air leaks and coolant/anti-freeze to leak into the cylinder ahead of the injectors. Tell tale signs can include rusty spark plugs on cylinder 1 and 4, sometimes even all four, lumpy idle or misfiring, high emissions, jerky acceleration and deceleration when coming off the accelerator, anti-freeze around the inlet manifold, unburnt fuel and possibly destroyed catalytic convertor.
  
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[[Inlet manifold gasket failure]]
  
 
[[Category:Engine]]
 
[[Category:Engine]]

Latest revision as of 19:10, 5 September 2011

Misfire

Steady Misfire

In the case of a steady misfire, isolating the misfiring cylinder is the first step in diagnosing the problem.


Items that can cause a misfire:

Loose/disconnected HT Leads

Check they are all attached properly! (Cured my misfire anyway....)

Moisture in Distributor (Dizzy) Cap

Unscrew, check for moisture, dry off.

Spark Plugs

Spark plugs

Coil Packs

Coil packs

Throttle Position Sensor

Throttle Position Sensor

Lambda Sensor

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.

Head gasket failure

Inlet Manifold Gasket Failure

The Inlet manifold gasket can fail and allow air leaks and coolant/anti-freeze to leak into the cylinder ahead of the injectors. Tell tale signs can include rusty spark plugs on cylinder 1 and 4, sometimes even all four, lumpy idle or misfiring, high emissions, jerky acceleration and deceleration when coming off the accelerator, anti-freeze around the inlet manifold, unburnt fuel and possibly destroyed catalytic convertor.

Inlet manifold gasket failure