A method for controlling engine idle in a vehicle having a motor connected
to the engine through a power transfer unit is provide. Upon receiving a
neutral command, the engine torque is commanded to approximately zero.
The motor torque is adjusted to maintain an approximately constant engine
speed as the engine torque is reduced. The torque from the engine
transferred to the vehicle wheels is at or near zero. When the torque at
the vehicle wheels is non-zero, a second motor is used to cancel the
torque output from the engine so the torque at vehicle wheels is zero.
When the engine torque has reached approximately zero, or when a
predetermined amount of time has past, both motors are shutdown, and all
of the remaining engine torque is transferred to the first motor through
the power transfer unit.