Misfire counters

How to act:

  1. Plug ELM327 adapter into OBD socket
  2. Start diagnostics software (for example: Touch Scan or Scan Master ELM)
  3. Open OBD mode 6 (‘On-board monitoring’ for Touch Scan; ‘Monitored test results’ for Scan Master ELM)

 

Disclaimer: as usually – no information from manufacturer regarding algorithms, all information gathered from analysis and observations.

 

Each cylinder has misfire counter outputs, and they contain two kinds of information:

a) counter of misfires for actual session;

b) counter of misfires during sessions.

 

Counter of misfires for actual session is zeroed, when the driving session is started.

Counter of misfires during sessions is calculated as following: long_count – 1 + 0,1 * act_count, where act_count is count of misfires for previous actual session, but long_count is counter during sessions.

(some resources describe relevance: 0,9 * long_count + 0,1 * act_count).

Sample: the counter of actual session is 33, the counter during sessions is 2. Starting new driving session, the counter of actual driving session will 0 (it is being zeroed), but counter during sessions will be: 2 – 1 + 33 * 0,1 = 4.

 

The image: how the counters of actual session and during sessions are placed.

For N53 series engine: last 12 lines;

For N43 series engine: last 8 lines.

 

Interpreting the results:

  • Misfire counters during sessions should be 0. If some of these counters are different from 0: corresponding cylinder has problems with ignition.
  • Misfire counter of the actual session should be close to 0. Acceptable values: up to 5 during the long driving session (more than an hour).

 

Exception: some MSD80 software releases are very sensitive to the uneven road. Misfire counters may have increased values after driving on the uneven road.

 

 

How to delete misfire counters.

If MSD80 has error message 3104 recorded (uneven run, Stratified charge) – when you delete this error message, the misfire counters are being deleted.

 

If the error message 3104 is not recorded, the counters can be deleted in following way:

a) engine OFF;

b) engine ON.

Repeat the procedure, until all counters of misfires during sessions become 0 (the counters will decrease with speed – 1, till value of 0 will be reached).

 

Related entries:

Uneven run. Rough run. Smooth run.

Specific features of MSD80

3104. Problem solved. Or not?