fast idle test?

[sierra3dr]

Hello all again,
how long is the fast idle kept on for,and I am assuming the reading taken,is when the gases have settled?

[chippie]

From memory of watching when my cars go for test….

For a BET, 30 secs is the duration for fast idle with the engine speed at 2500rpm, followed by a settling time of 30 secs.

The readings should be: CO less than 0.2%, HC less than 200ppm and the lambda sensor should be reading between 0.97 to 1.03 which is a function of Oxygen content in the exhaust gases….

Maybe a MoT tester member can confirm the above?

[sierra3dr]

Thanks chippie 👍 I can never remember the max😁 I refer to this website www.petercoopercarrepairs.co.uk/new_page_3.htm