Why is my 1.8T AUM running so lean stationary

[DiFeE]

Hi I have a question? The question is about a golf 4 1.8T AUM 2001, I just solved the problem as the car rocked like crazy and was not drivable, turned out a bolt was missing from my downpipe and the gasket was popped, well that's solved now and the car is running again, I had a bosch air mass meter, unfortunately it was broken because it only measured 90g/s with full throttle, then I put a strong air mass meter on it, the car has never really driven well with this air mass meter because when gas kicks loose he with this air mass meter, when the car was made I started driving and I went to look at the values ​​and it struck me very much that the car is really running too rich and when I'm talking about huge then think of between -15 and -25 and I logged this on the cruise control with 100km/h, now I also bought a new air mass meter from pierburg, the car drives well with it and measures a bit better than the stark air mass meter, before I put pierburg air mass meter on it I put the battery for 2 hours had it loose to reset the fuel trims, I then started driving with the pierburg air mass meter and with this it drives perfectly and boosts well, tested again with 100 km/h on the cruise and now it measures perfectly -5 and +5 so perfect and now just drives economically, but now I notice something different with this pierburg air mass meter when I let the engine idle it runs very lean think of +15 +25 and this is also audible you hear the engine really completely different running not really smooth and smoothly say it does not swing or something just keeps running nicely at 750 rpm, but why does my car run so very lean with idling and driving not at all and just perfect? After that, the stark air mass meter was put on again and it went worse with it he kept running lean for a while but when driving he went really too rich with stark all the time as I just said, I made 2 videos, these are videos of driving with the stark air mass meter and the pierburg air mass meter and there you have to pay attention to the lambda what it measures. I have looked at everything and checked I have put the car under pressure and smoke is not coming out anywhere so I have no vacuum leaks, I also have 0 error codes in my car, so why is the car suddenly running so lean it makes me crazy.

Video from live data pierburg air mass meter https://www.youtube.com/watch?v=bh2zRDHgD6Y
Video from live data stark air mass meter https://www.youtube.com/shorts/GxGPw7TxNDA

[al70]

i solved a similar problem while back by changing O2 sensors, car had no fault codes

[motorsportsz]

i solved a similar problem while back by changing O2 sensors, car had no fault codes

+1
Also had a similar issue ending up being a O2 sensor.

I'd start off checking for vacuum leaks before going for O2 sensor. Smoke test it

Sent from my SM-G973F using Tapatalk

[raceshadow]

Hi I have a question? The question is about a golf 4 1.8T AUM 2001, I just solved the problem as the car rocked like crazy and was not drivable, turned out a bolt was missing from my downpipe and the gasket was popped, well that's solved now and the car is running again, I had a bosch air mass meter, unfortunately it was broken because it only measured 90g/s with full throttle, then I put a strong air mass meter on it, the car has never really driven well with this air mass meter because when gas kicks loose he with this air mass meter, when the car was made I started driving and I went to look at the values ​​and it struck me very much that the car is really running too rich and when I'm talking about huge then think of between -15 and -25 and I logged this on the cruise control with 100km/h, now I also bought a new air mass meter from pierburg, the car drives well with it and measures a bit better than the stark air mass meter, before I put pierburg air mass meter on it I put the battery for 2 hours had it loose to reset the fuel trims, I then started driving with the pierburg air mass meter and with this it drives perfectly and boosts well, tested again with 100 km/h on the cruise and now it measures perfectly -5 and +5 so perfect and now just drives economically, but now I notice something different with this pierburg air mass meter when I let the engine idle it runs very lean think of +15 +25 and this is also audible you hear the engine really completely different running not really smooth and smoothly say it does not swing or something just keeps running nicely at 750 rpm, but why does my car run so very lean with idling and driving not at all and just perfect? After that, the stark air mass meter was put on again and it went worse with it he kept running lean for a while but when driving he went really too rich with stark all the time as I just said, I made 2 videos, these are videos of driving with the stark air mass meter and the pierburg air mass meter and there you have to pay attention to the lambda what it measures. I have looked at everything and checked I have put the car under pressure and smoke is not coming out anywhere so I have no vacuum leaks, I also have 0 error codes in my car, so why is the car suddenly running so lean it makes me crazy.

Video from live data pierburg air mass meter https://www.youtube.com/watch?v=bh2zRDHgD6Y
Video from live data stark air mass meter https://www.youtube.com/shorts/GxGPw7TxNDA

The first thing is, use only OE or BOSCH sensors. Checked the vacuum hoses. There are check valves on the hoses and these will cause a lot of problems several times, also check the PCV valve and complete crankcase breather, check the Blow off valve for punctures or leaks. Check the fuel pressure to see if it is still 3 bar. Check the MAP sensor, whether the temperature and pressure in the intake manifold at idle correspond to 970-1000 mbar. If necessary, try to measure the vacuum behind the throttle about -0.7 - -0.8 bar.

[DiFeE]

With sensors I know that Bosch is the oem brand, but in recent years I have noticed that these sensors are just fairly weak and break more often or measure less values, have spoken with other tuners with built 1.8t engines with 500hp and use them all pierburg and never want anything else, so that's why I started using pierburg. Just cleaned the throttle body as it was very dirty inside.