Audi misfire

This bulletin applies to 2008-2014 Audi A3, A4, TT, A5, A5 Cabriolet and Q5, and 2012-2014 A6 vehicles. A MIL may be on with P0300 and/or P0301, P0302, P0303, P0304 (cylinder misfire detected), along with a rough idle. The engine may have reduced performance without significant loss of power or stalling.

Because there are a number of different misfire faults (unrelated to ignition coil operation) that could cause the MIL to illuminate, proper Guided Fault Finding (GFF) misfire diagnosis must be followed before any ignition coils are replaced.

Ask the customer the following questions about the symptoms of the condition and when it occurred. This information will be necessary for duplicating the condition during service:

-          In what situation does the condition occur? (while turning, etc.)

-          Under what environmental conditions (road conditions, weather, temperature, start conditions, etc.) does the condition occur?

-          What is the operating situation of the vehicle (activated electrical equipment, gear selected, etc.) when the condition occurs?

  1. Read the data memory of all engine control units and note the environmental conditions on the DTC log. If there are other entries in addition to combustion misfires, address these other areas before addressing the misfires. If DTC P0301 – P0304 is accompanied by DTC P1250 (fuel level too low), it is likely that the faults occurred due to a low fuel level and not due to coil malfunction. Review all applicable TSBs related to cylinder misfires and ECM software improvements before diagnosing the misfire condition. For example, if the data shows that the DTC was set during cold start, search ElsaWeb for TSBs related to cold start misfires.
  2. Try to duplicate the customer complaint based on the environmental conditions at the time the DTC was set. The freeze frame data gives important indicators for the traceability of the complaint, particularly if it occurs sporadically or at cold start.
  3. Review the vehicle repair history for previous misfire service or other service that could be related to the current complaint.
  4. Observe the requirements of GFF. Perform GFF in full according to the proposed sequence. Do not skip any steps.
  5. Complete GFF correctly and set the readiness code. Doing so will ensure that no subsequent faults occur due to the misfire.
  6. In the case of single cylinder misfires, before replacing components, exchange the coil to determine whether the condition migrates to the other cylinders after the coils have been exchanged. NOTE: Always use special tool T40039 to remove ignition coils. If the misfire migrates to another cylinder with an exchanged coil, replace only the affected coil.
  7. Verify the repair under the same conditions (engine speed, engine load value, vehicle speed, coolant temperature, intake air temperature, ambient air pressure, voltage at terminal 30, etc.) as noted on the DTC log.
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