Almost new car! This time – a story of BMW F36 435i, 4-door coupe, with N55 series engine and as if low mileage – only around 90’000 km. The car has recently arrived from Germany and will soon find its new, happy owner.
At first glance, the car looked nice – exhaust nozzles promised that the Performance pack could be installed. Isn’t it a good “catch”?
Faithful thou – when the car was lifted, we had to detect that the exhaust was poorly welded. The BMW dealer wouldn’t do that. In addition, there were no appropriate labels on the engine hood nor upgraded measuring units in the Sport displays in NBT. Not even talking about any documented proof. It becomes clear that no Performance pack is installed.
When pressing the accelerator pedal, a “popcorn” sound appeared. Oh, what an exhaust!
The inspection of the error message list indicated 40+ error messages, and the car hadn’t seen the computer diagnostics for a long time. This relates to DME; there were error messages regarding misfires in 5 of 6 cylinders. Here are the misfire counters:

The car has run idle for 5 minutes, and a range of misfire events registered (especially considering that the Bosch DME records misfires very unwillingly). During previous sessions – tens of misfires in each cylinder; in the first cylinder – even hundreds of misfires during each session!
At the same time, live data indicated that the fuel mixture is correct; the mechanical efficiency of cylinders – is identical. This is good news.
The decision to check the spark plugs was made. It turned out that they were not replaced since the car was “born”. So – the spark plugs should be replaced, and the ignition coils in the 1-st cylinder (sure is “tormented” due to countless misfires and increased air gap of the worn-out spark plug). After replacing the spark plugs and the ignition coils, the “popcorn” sound disappeared, and the car’s performance became quiet and calm. Most part of the charm – is gone as it has never been there! Misfire counters – all are 0, problem solved!

After a short moment, the car was driven to the TI, where it got two remarks 2 regarding exhaust gases (which means – the TI is not passed, it should be repeated after 30 days). Here is the protocol of TI regarding exhaust gases:

What do we see in this protocol?
The average fuel mixture is correct; Lambda is precisely 1.0. There is no reason to think that suddenly a large disbalance of cylinders has appeared, accordingly – before the CO catalytic converter, the fuel mixture combustion products should be correct. Also, HC/CO proportion confirms – no misfires, but both (CO and HC) correspond to the engine readings without CO catalytic converters.
Obviously, the CO catalytic converter is either damaged or eliminated. Good news – for this engine, a new OEM catalytic converter is relatively cheap – it costs around EUR 1200.
Bad news – it is logical that the next buyer will purchase this car without this catalytic converter. The reseller of the car honestly told me that the catalytic converter would not be bought. Either the ethanol will be filled in the fuel tank or some TI employee bribed – the options are not a secret. One more stinking car will be added to the car park out of our country.

This time more about the technical aspect.
First – the cars with a damaged exhaust system are in mass purchased from the developed countries. The reseller also admitted it, adding that in the last “portion” alone are several cars with “upgrades”; without this BMW – also an Audi with a “straight tube”. It is only logical – after such “upgrades”, you can not pass TI in DE/NL/FR and other countries; accordingly – such cars are sold to the “export”.
Second theme: is it possible to “kill” the CO catalytic converters during 100’000 km due to unchanged spark plugs? Easy! Without any additional effort! In addition, you have to understand that it is enough of 5 .. 10% of the initial performance of the CO catalytic converters to pass the TI. In this example, the performance of the CO catalytic converters looks complete 0.
Third – what should be done in this situation (tried to pass TI, but the exhaust gas test indicated a too high an amount of CO/HC)? Check the misfire counters and fuel mixture. Take the car to the service, which has the equipment to measure the exhaust gases. At the same time following things should be evaluated: engine temperature, fuel mixture, and performance of cylinders. If these are ok, but the exhaust gases are still proportionally above the norm – unfortunately, the CO catalytic converter is damaged. Or eliminated. And you can expect certain expenses.
Quite an unpleasant story – and someone will buy this car with a “Performance pack” and only later will find out that there is a “pack” and neither the CO catalytic converter.