This time: N54 series engine. The complaints of the car owner: sometimes – permanent vibration in idle, sometimes – uneven performance. Everything that can be changed is replaced: injection coils, spark plugs, injectors, etc. The effect – zero. 

Let’s see live data.

Fuel mixture – enriched. At the same time – corrections are slight. The car owner says he has performed the smoke test of the inlet manifold and the pressure test – no air suction detected!

Yes, here we see – the fuel mixture (especially at the 1-st bank) is rich; it is also confirmed by the control probe. Additional problems – not confirmed Offset type LTFT, also the ref values of the multiple LTFT can not be found in the regular registers.

This time a strongly enriched fuel mixture in the 2-nd bank. How so?

And now – incorrect fuel mixture in both banks!

 And after a moment – again, the problem at the 1-st bank!

Here even more extreme view. The multiplicative type (flowrate) adaptations of all injectors are strongly moved to the side of lean fuel mixture, at least for three – the adaptations are outside the allowed range! The LTFT of the bank, which should work “at first”, is very close to 0! Why so? Even more – there are no even error messages regarding overreaching the allowed ranges of the corridor!


Oh, this “insignificant” error message is connected with the engine “tuning”. Sometimes the other error messages regarding boost and other things appear…

What can I say to the owner of this car? Unfortunately, the “improvements” of the “chip tuners” have completely damaged the DME management. There is nothing to wonder about periodic vibrations. DME is not able even to maintain more or less correct fuel mixtures in the banks. Without any illusions, the CO catalytic converters will have to be changed for new ones quite soon. Passing the TI will be the smallest of all problems. 

Additionally, the fuel maps are modified to increase the injected fuel amount with the idea – more fuel: more power. Unfortunately, DME has reduced all these tries to 0, reducing the flowrate adaptation map values of each injector. In true: the increase of power and torque is zero, but there is a bonus – vibrations, shivering, incorrect fuel mixture! 

This masterpiece was performed by a well-known and respectable chip tuning company. I have to admit – impressive!