Without a long intro. I drove along the great roads of Poland. Summer, outside temperature around 30 °C. By Lodz, there was a road repair, so I had to push at a slow speed for a while.
Suddenly, the Check Engine light lit up in the KOMBI; in the NBT display, there was a drivetrain malfunction error message. Yes, the problem could be felt – the Engine vibrated on the go, its power was reduced. The most interesting thing is that before the error message appeared, there were no symptoms, no white smoke was visible (a typical symptom in case of problems with any cylinder).
I stopped at the first opportunity and connected to ISTA. Yes, the well-known cylinder No.6 has crashed. But the error message is different. This time, the error message is regarding Combustion time: 144018. Let’s see the attributes of the error message:
As we see, the Combustion time was 0ms. What does that mean? DME has determined that there was no high-voltage “blowout” on the power transistor C (collector)!
How is that possible?
If the connection to the primary winding of the ignition coil is lost, another error message would be recorded: the DME would notice that the connection is interrupted (there is no +12V voltage on the transistor’s C during the passive period of the cycle). Conclusion: The connection of the ignition coil is fine, but there is no energy in its secondary winding.
Obviously, the energy is leaking somewhere. The energy can leak in the ignition coil itself or outside it – for example, along the spark plug insulator.
It is clear – if there is no energy necessary for ignition, there will be no spark. If there is no spark, the fuel will not combust – problems (misfires) guaranteed. The reaction of DME by switching off this cylinder was correct.
And what is pleasant – there are no patent wars/limitations regarding this functionality (unlike misfire detection by flywheel mechanical energy). DME reacted quickly. No group misfires, no fuel leftovers in the exhaust, not even talking of smoke.
After restarting the Engine, DME restored normal Engine performance. Check Engine disappeared, and the car performed as if nothing bad had happened.
During the next 500 km, identical crashes repeated three/four times more. Symptoms, error messages – 1:1. It should be noted that for several times the problems occurred on the go – (repeated) overheating of the ignition coil will not be the culprit this time.
When I reached my home country, I immediately (several new ignition coils are stored in the private warehouse) replaced the ignition coil of cylinder No.6. Now more than 30.000 km have been driven, and the defect has not repeated.
In the next blog entry, I will discuss how the test of the damaged ignition coil went and the reasons that could cause this defect.
