Idle gradually decrease

[mamun22s]

I have a vitz 2000, 2NZ-FE. Recently, I replace a the engine from a after market. I have faced a new problem. Car idle decrease gradually decrease. And one of servicing person suggest me to open (-) battery terminal and reconnect after 5 minute. That actually solve my problem temporary. After run the car around next 100 km same problem arise again and engine stall on idle. There is no error code on OBD.

Can any one suggest me the reason and the solution.

-Thanks

Mamun

[lupetnen]

hi mamun seems to me you have a dying fuel pump if the engine gradually decreases in idle.

[mamun22s]

hi mamun seems to me you have a dying fuel pump if the engine gradually decreases in idle.

Thanks lupetnen for your replay. As I mention my problem totally solve after (-) battery port for few days. If it is for fuel pump it would happen always. But once after I open (-) battery port everything going normal for few days.

[Bluevitz-rs]

The throttle stop might be set to low on that motor. What RPM does it idle at? Can you make a short video?