Idling rpm up and down

[Max1917]

Hi all just bought an 06 jazz sport cvt ,been standing for about 18 months,all seems fine but when engine warms up the revs fluctuate when it’s in park,anyone know what causes this please tia.

[tostibrand]

Do you have A/C on? on my 5spd manuel if i have A/C on it will rev up a bit (couple hundred RPM) every like 10 seconds and come back down. With A/C off this does not happen.

Another cause could be low coolant