vRS MK3 Diesel

[whooshs]

What should the at rest tickover be - mine's at 1000 rpm and if in 5th it starts to run away a little?

[Cammy5477]

Mine too

[Exeterj]

1000rpm if its doing dpf regen but i little less normally IIRC

[Gabbo]

The idle speed varies for many factors.A hot engine should be around 800rpm.

 

If the engine is cold, the idle speed is increased progressively based on the temperature.

If AC is enabled, idle speed is sometimes increase to improve the compressor performance.

If the clutch is released slightly the idle speed increases anticipating a pull-away.

If the DPF is regenerating, the idle speed is increase to help maintain airflow & temperature through the exhaust.

 

 

I'm not really sure what you mean by "in 5th it runs away a little"..

The idle speed control is active even when the gear is engage & will drive the car at idle (trying to prevent the engine from stalling).

In higher gears it is harder to maintain a low speed so the idle speed controller has to work much harder to keep the engine revs up which can sometimes be felt as a slight acceleration if e.g. the road gradient changes.

[Gadget007]

Hot idle on mine (as read using a Bluetooth OBDII dongle and the Torque App) is around 780rpm. if it is doing a DPF regen or is cold idle is around 1000rpm.

[whooshs]

Ok - if i go to 5th at 30mph - the car speeds up slightly, fuel consumption drops 

it's fine in 4th

but rpm at 1000

if rpm were around 800 at idle it would be fine

[Gabbo]

if the vehicle is in-gear the idle is higher than 800rpm (something like 1000rpm).

I would have to check on my car at the weekend but in idle-drive (idle-speed but with the gear engaged) in 5th gear I would imagine 1000rpm puts you higher than 30mph which is why you feel the car is accelerating.

 

To understand how the idle-drive works, fine an empty car park or long open road where you can safely drive slowly.

Pull-away and release the clutch completely.

Release the accelerator pedal & do not press the clutch or brake.

Let the engine revs fall to idle & the ECU will maintain an idle speed of 1000rpm (the engine will not stall) & it will continue to drive happily on its own adapting to the gradient or load to maintain a speed of 1000rpm.

 

It works the same in all gears but obviously it gets progressively more difficult for the engine to maintain the speed in longer gears.