Team-BHP - View Single Post - Idling Time during Morning Start for MPFI Vehicles

Roshun · 7th April 2006, 16:27

The revving engine during cold starts is a normal phenomenon. Happens with my WagonR as well.

I usually start it, wait for about 1 min, while I adjust the mirrors, seat, put on glasses etc... and then gently drive off. It usually warms up by the time I reach the first traffic light. When I stop for the light it still revs for about 20 secs, before gradually settling to a whispering 800 rpm.

The reason this happens with most MPFI cars is this... since they have no choke (carburetted cars rev when the choke is pulled), the ECU senses a cold engine - and makes the fuel slightly richer - while opening the throttle flap marginally. Once the engine is warm it settles down.

The only thing I find odd about the ECU's logic is that if the car is moving, it does not reduce RPM (even if you let the engine idle and let the car roll in neutral, while slowing down).

Cheers,
Roshun

7th April 2006, 16:27	#35 (permalink)
Roshun BHPian Join Date: Oct 2005 Location: Delhi Posts: 51	The revving engine during cold starts is a normal phenomenon. Happens with my WagonR as well. I usually start it, wait for about 1 min, while I adjust the mirrors, seat, put on glasses etc... and then gently drive off. It usually warms up by the time I reach the first traffic light. When I stop for the light it still revs for about 20 secs, before gradually settling to a whispering 800 rpm. The reason this happens with most MPFI cars is this... since they have no choke (carburetted cars rev when the choke is pulled), the ECU senses a cold engine - and makes the fuel slightly richer - while opening the throttle flap marginally. Once the engine is warm it settles down. The only thing I find odd about the ECU's logic is that if the car is moving, it does not reduce RPM (even if you let the engine idle and let the car roll in neutral, while slowing down). Cheers, Roshun