I can't figure this out. No one can. I have a 99 disco 1 with 120,000 miles. in the morning i crank it and it always is up at 2000-2500 rpm's. put it in reverse or drive and it drops to around 1000-1200 rpm's. lately if i stop the engine and crank it again sometimes it will idle around 750 and sometimes it will run high again and the crazy thing about it, is that some times when i've done a lot of turning the engine on and off it'll idle really low and when i put it in drive or reverse, it'll die.
so, i've cleaned the stepper motor. i've tried another one. no difference. i've changed out the entire plenum, including throttle body and cables. not difference. i've checked for a vacuum leak with carb cleaner and i've had a land rover mechanic check for vaccum leak. nothing found. is there something i'm missing. does anyone have suggestions. oh yeah, i've checked around the site, and i haven't found anyone with a high idle problem like mine. or a good solution. thanks for helping.

jason

 

Did you replace the steepre motor with a new one or a used one?

 

i found someone with a used one. put it on real quick and the same high idle. jason

 

If you know that the other one was good...then I would lean towards a vacum leak.
That is the only think that I can think of.

 

would a truck with a vacuum leak every run at a low idle? seems like when it's warmed up, it'll run low. does this give anyone any ideas?

 

Depending on the vacum leak it can run at a really low idle, not idle, or a really high idle.
Because it idles high when cold and then normal when warm I am guessing that the leak closes when whatever is leaking expands from the heat of the engine.
It expands and plugs the leak, when cold the leak is open again.