Misfires and exhaust gases

In this entry, an example of how the misfires affect the exhaust gases.

One of the owners of the vehicle with the N43 series engine installed the NOXEM, performed quick re-adapting of the engine, and went to the annual technical inspection. Unfortunately, unsuccessfully.

Here, the screenshot of the measurement of the exhaust gases:

The TI inspector has said that the measurement of the exhaust gases is terrible because of practically all measurement parameters are in the red zone.

But let’s see, what is the actual situation:

  • let’s start with the bottom data field: Lambda around 2.7. First conclusion – the engine runs in a Stratified charge. This is good news – DME considers that everything is fine with its systems!
  • CO indications are perfect – the measuring instrument was not able to measure anything!
  • O2 is oxygen: logically, the amount of it is increased because the engine runs in a Stratified charge with 2.7 times of oxygen leftover (this parameter is not measured: data are taken from the Lambda value).
  • CO2 is a carbon dioxide, its amount – smaller than it would be in the case of Homogeneous mixture mode. In my opinion is not correct to color the REDUCED amount of CO2 in red, but – let’s leave it on the measuring tool developers’ conscience.


  • CO = 0.00 %, perfect result;
  • HC = 171 ppm, increased  (max allowed: 100 ppm).

Already in other entries, I have mentioned:

  • increased CO: incorrect fuel mixture/partly burned fuel (too lean or rich fuel mixture, topical for Homogeneous mode);
  • increased HC: misfires – unburned fuel.

In this case, serious problems with misfires are confirmed by the DME error message list:

What information is given by this error message? Cylinder No.2 is turned off due to mass misfires.

  • the error message recorded for three times during 30km;
  • all three times: the engine was warmed up, the error message recorded in idle;
  • last time: the engine was running in Homogeneous mode, the fuel mixture was correct (none of the injectors of the current banks was leaking).

Obviously, there are problems with the ignition system: ignition coil, the spark plug of the cylinder No.2.
New OEM spark plugs are recently installed, so – the ignition coils should be checked.
The owner of the car was not wasting time – installed a new Bosch ignition coil and went to the repeated exhaust gas test.

Here, the results of the repeated test:

  • the engine again works in Stratified charge, Lambda 2.0;
  • CO = 0.00 %;
  • HC = 0 ppm! Problems solved! A perfect result!

Here I have to remark that a perfect result does not mean that the test was successfully passed. The owner of the car reported, that also repeated test was not counted, because, according to the TI, half of the data are incorrect. In this case, my blog and the information in it regarding the specifications of these engines came in help. The owner of the car visited the TI for the third time with a computer in his hands. It helped – the TI inspector acknowledged that he has no counter-arguments and issued the TI label.