Problem with Lambda Control (Oxygen Sensor) on Seat Leon Cupra 1.8 T BAM

Hello everyone,

I'm having a rather strange problem again. I have a Seat Leon 1M Cupra with a 1.8T engine (MKB: BAM), which is the 225 hp engine.
The problem is that the CO content is much too high. The AU tester shuts off at 10% CO!

While troubleshooting, I encountered Lambda values where the expected value (SOLL) was 0.65, but the actual value (IST) was 0.75. It's no surprise that he's getting too much fuel.

Now my question: Could a technical defect be the reason for the lambda sensor's target value being significantly reduced, or was the engine being operated in a "Schmu" mode (a term likely referring to a specific, possibly unconventional, operating mode)?

The car has an engine problem; I haven't seen it running yet. I don't know if anything has been done to the engine control unit, but I wouldn't be surprised if it has.

All the mass airflow sensors are working correctly. I've also already checked the vacuum system and the intercooler system.

If the issue is related to the lambda control, can I use VCDS to modify the target value or reactivate the lambda control?

Thank you in advance for your help.
Best regards,
Leon.

Hello,

"Engine damage," catalytic converter, and oxygen sensor: still functional or possibly fouled with oil? Is the engine safe and working properly?

Please check the signal from the oxygen sensor in the measurement blocks.

You cannot change the target values using a diagnostic tool.

Best regards, Rainer.

Hello,

So, the engine damage was a broken connecting rod, so it's unlikely that it burned oil.
"Kat" is from a donor vehicle and was fully functional until the last inspection. The Cupra comes standard with two metal catalytic converters.
The engine does not burn oil or water, and it has no misfires or ignition problems. The spark plugs are new.

I'll double-check the Lambda signals and get back to you afterwards.

Best regards,

Okay, so the Lambda values are off the charts, but the Lambda voltage of the control sensor is also far too low. It could be due to the low target and actual values, or am I mistaken?
The ignition timing is also very advanced; it's already at 35 degrees before top dead center (BTDC) at 2500 RPM.
Here's another photo attached. I can also upload the Autoscan file if needed.

Best regards,
Leon.

Hi,
What values do the sensors provide for the temperatures (engine, intake air, etc.)?
If the engine control unit (ECU) detects that it is too cold, it will enrich the fuel mixture and likely also advance the ignition timing.
That's one possibility.
hg
Herbert.

"Based on the numbers, you can already tell that it's performing extremely well." It makes your eyes water just standing near the exhaust fumes.

The premature ignition could be caused by the lack of boost pressure and the relatively low compression ratio, combined with an overly rich fuel mixture. Once it's warm, the knock control will adjust accordingly to prevent early ignition. In the current operating state, full early ignition can be applied. I wouldn't worry about this for now.

I'm assuming that the control system is excessively complex, and that the BAM (likely referring to a specific device or system) uses a 4-pole control probe. Typically, with these probes, you'll find the probe signal between pins 3 and 4. Usually, there are two cables of the same color and two cables of different colors connected to the probe, and you need to use the two cables of different colors. At Bosch, gray is for the positive probe (+) and black is for ground.

You should try measuring the voltage between pin 3 and pin 4 with a multimeter while the engine is warm. If the engine is running too rich, you should measure a voltage above 0.6V. If that's the case, you might have a wiring problem. If it's not, your sensor might be broken.