rpm will go up and down

[brano]

i am the owner of a mazda 3 and the problem with my ride is when i am waiting at the signal or anywhere else( car is on but not working) the rpm goes up and down even when i have my foot on the breaks.

this is scary

how can i fix it

[alexd]

If car doesnt need service. Check sark plugs, fuses and relays.

Then coil and HT lead some elctrical fault cold be there.