Thank you guys, maybe surging its not the correct word, english is not my native language. I'll try to explain my best...

It's definitely more notorious when the car is warmed up. while driving at constant speed around 30-60 km/hr, there is an on/off (either electric or fuel) and a gurgling sound.. the car jerks. if i push the accelerator pedal, it gurgles for a millisecond and immediately push correctly. If i push the pedal it goes ok, its noticeably while maintaining the speed; low speed.

While maneuvering to park, for example, If when I push the gas pedal the engine may turn off, I have to regulate and push t hard so it doesn't die.

The previous guide is very useful. I'll check as much as i can.

To remove the AAV, should I remove the radiator cap to avoid liquid spilling out? any other important consideration?

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1972 W108 280SE 4.5
1977 W116 450SEL
1981 E12 528i BMW