Misfiring
Read the instructions below then
start the fault diagnostic procedure.
Symptom: Misfiring
Fault symptoms
Misfiring
Conditions
The following conditions apply for this fault symptom:
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No diagnostic trouble codes in the car with the symptom description in question.
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Diagnostic help
Start fault diagnosis by changing the spark plugs and then use the misfire counters to determine whether one or more cylinders are misfiring.
If only one cylinder is misfiring, concentrate fault diagnosis on that cylinder and check the compression, the ignition trigger from the control module, the ignition discharge module and, finally, the injector.
If several cylinders are misfiring, check components and cylinders that are common to all the cylinders. First carry out a general check of the leads, connectors and hoses, and then a thorough check of the compression, ignition and fuel system.
Diagnostic tool functions related to this fault are:
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Multiplicative adaptation, in %
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Additive adaptation, in mg/c.
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Short term fuel trim, in %.
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Purge adaptation, in %.
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Airmass deviation from calculated, in %.
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Activation of misfire counter resetting.
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Activation of ignition trigger.
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Activation of injector test.
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Activation of pump test.
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See also the description of activating functions under ”Fault diagnosis, general” for more information.
Check the wiring
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Note
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Jiggle the leads and in-line connectors at various points and in different directions to detect any intermittent breaks or short circuits in the wiring. Observe the multimeter, test lamp or diagnostic tool while doing this.
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