engine run up in icing condition

[ulisse]

good day
I'm a bus driver and recently I was confused by the meanning of the run up in icing condition

as far as i know if you are experiencing some vibrations during the run up you should assume that the engine(s) are iced and to avoid damage due to ice shedding and ingestion you should keep at idle and return to gate to remove it in another way

any info is appreciated

thanks