Cat Purring, White Smoke from Exhaust System

Hello friends, I need your help. I have a 1.8t AJQ engine that has been chipped.
Recently, my car's headlight broke down while I was on the highway, and then...
I got a new one (with a new serpentine belt). Shortly after, the yellow ESP warning light illuminated on the instrument cluster in the morning, so I pulled over to the right, turned off the engine, turned it back on, and everything was fine again. Later, I read the error codes and cleared the error.

00812 Release switch for magnetic coil, brake pressure 35-10, intermittent issue.

"I discovered and then deleted something. Now, the car stood outside in the cold for 3 days, and when I started it, it sputtered and sounded very unhealthy (making a very loud knocking and gurgling noise), and then it emitted some really foul-smelling exhaust. I thought that maybe due to the moisture/cold, I should check the connectors."
Air mass meter, intake air temperature sensor, and turbocharger boost control valve (N75) were sprayed with contact cleaner (from ATU, they only had one). However, the contact cleaner was strangely oily and didn't seem to thin out, and the car was running even worse. I then sprayed the connector contacts with brake cleaner and let them dry. After that, it ran normally again. I checked it again with VAGCOM while it was stationary, and it didn't show any errors. I thought I'd take it for a short drive, but the car was accelerating poorly, as if something was holding it back (like a stuck brake). There was also a buzzing noise under the car near the catalytic converter. The smoke coming from the exhaust pipe increased, and the fuel consumption rose steadily to 15.9L. I drove about 30 meters before I got worried, and I parked the car again. I then read the error memory again, but there were no results.

Can anyone tell me what this could be? The spark plug is burning out, the catalytic converter might be bad, or the readings could be inaccurate due to the contact spray. But please don't say it's the head gasket.
When I parked, it was already dark, and it was difficult to see anything in the engine compartment. However, there was no smell of gasoline or exhaust fumes. I opened the coolant reservoir and smelled it – it smelled normal, like coolant, and not like oil.
Over time, I also noticed that the fuel consumption was slowly increasing (but still within an acceptable range for the city, around 11-12 liters), and that condensation was forming at the exhaust tip. I have a complete exhaust system from the turbocharger, with a 200-cell high-flow catalytic converter, and I thought that was normal. Finally, I also noticed that a lot of pressure was coming out of the exhaust, and it didn't smell like exhaust fumes at all, but more like gasoline.
I'll drive over to the friendly mechanic (who fixed my alternator) tomorrow in a different car and explain the symptoms to him. I don't feel like driving that car.

I hope you can help me; I'm just having terrible luck with this car.

It indicates unburnt gasoline, suggesting an overly rich fuel mixture. Temperature sensors should be checked with VAG-COM to verify their readings when cold. Check if the oxygen sensor is functioning correctly when warm. Also, check the timing belt.

Thank you for the response.
Temperature sensor: Sorry, I forgot to mention that I also sprayed it with contact cleaner, but I forgot to clean it with brake cleaner. Do you think it's because of the contact cleaner? That stuff was really oily. Before this, the car also smelled like gasoline coming from the exhaust and it took a very long time to warm up. Should I just get a new temperature sensor?

Temperature sensors were checked using VAG-COM for plausibility when cold. Does the oxygen sensor function correctly when warm? Also, check the timing belt adjustment!

How should I proceed? Should I use a multimeter to measure the temperature sensor, or VAG-Com (which measurement block)? Shouldn't the temperature sensor be stored in the error memory? I think the lambda values were within the normal range. How do I check the timing belt? Sorry, I'm a beginner when it comes to working on cars.

Temperature readings are best obtained using VAG-COM mb 7. I'm not entirely sure if this applies to gasoline engines. Ideally, all values should be the same (within +/- 3°C) after the engine has been idle overnight. Error messages in the diagnostic memory usually only appear if the temperature sensor has a complete failure and loses contact. More often, the sensor provides incorrect values to the control unit, which prevents an error code from being set because the control unit "believes" the sensor's reading. For example, if the actual temperature is +3°C, the sensor might report -32°C.

"ZR adjustment: Most often, the timing mark on the transmission is visible through a small hole, located near the crankshaft after the ZR cover is removed, and is indicated by markings. You may want to search online for instructions on how to adjust the ZR for your specific engine type (e.g., by searching on Google)."

Hi, thanks for the reply. I'll take your advice into consideration. What should I do with the oxygen sensor? Where should I check the value, or can it only be checked when the engine is running and under partial load? I stopped by VW yesterday (in a company car), but they were closed. I quickly mentioned my problem to a workshop employee who was just leaving. He told me not to drive the car, but to have it towed to them so that more doesn't break, because they have special measuring devices that can provide a more accurate diagnosis, and it's not really possible to do that with VAG-COM. I'm not sure if he's just trying to get more money out of me. In any case, I've cleaned the connectors with brake cleaner and haven't started the car again yet, I don't want anything to explode.

Das Unwissen wrote:

Hello, thank you for the reply. I will consider your advice. What should I do with the lambda sensor? Where should I check the value, or can it only be checked when the engine is running and under partial load?

Check the Lambda sensor with VAG-COM when the engine is warm; the reading should fluctuate rapidly.

Quote:

He told me not to drive the car, but to have it towed so that nothing else breaks, and to take it to them because they have special equipment that allows them to examine it precisely, which isn't really possible with VAG-COM. I don't know if he just wants to drain my wallet.

Vag-Com can do just as much, or even more, than the official VW tester! So, that's complete nonsense...
Before you start the engine, make sure to check the valve timing first! This is the safest way to proceed. The engine might only stall due to an overly rich fuel mixture, which could cause the spark plugs to become wet. Once the problem is resolved, I recommend changing the oil, as unburned gasoline may have entered it.