Been tinkering around on the motor this afternoon trying to sort this one out. Range Rover 3.9 when I start her up the revs fluctuate then settle. a few times in really cold weather she has stalled after stopping when cold. Revs are staying a bit high on tickover 750ish instead of 550ish. Checked for air leaks, sticking throttle, cleaned air sensor. Any suggestions. Usually feels like new just at moment feels a bit sluggish.