my 99 discovery is idling high. in the morning it starts out at about 2500-3000 rpm's. as it warms up, it usually calms down to about 1200 or so at stop lights. when i am at my destination and put it in park it jumps back up to the 2000's again. i've checked for vacuum leaks, replaced the stepper motor with another used one, cleaned the throttle body and throttle plate and had a mechanic to an induction cleaning. any other advice on this one.
thanks for any help you can give.jason

 

You need to go thru and recheck, when cold, especially for a leak. How did you already check?
Are you sure neither of your t/cables is not hung up?

 

try adjusting you base idle, just make sure you dont go too low as to cause it to stall

 

I would only make that adjustment if all else fails, cause bottom line there will dtill be a problem going on that should be corrected.

 

ok so we checked for vacuum leaks by just eyeballing it.just rechecked it again this morning. t cablesseem fine. like is said beforewe changed out the stepper valve. cleaned throttle body and plate, did an induction cleaning, and it still idles high. to go into a little more detail, it always starts high in the morning, then for the rest of the day it doesn't idle quite as high, maybe 1200 rpm's. sometimes it even idles at 700-1000 rpm's at a stop light but as soon as i put it in park again, it goes back up to 1200-1500 or so. it's definitly jumpy. computer problem maybe?

 

any chance rebooting or reflashing my computer would help?

 

You can't check for a vacuum leak by looking at it. When the engine is stone cold, spray carb cleaner along the manifold seals, if there is a leak, the carb spray will get sucked in and the idle will go even higher for a second or two. Don't do this with a hot engine, or you will need to put out the fire afterwards.

 

ok so we pumped some smoke in to eyeball if there were any vacuum leaks. nothing. can't think of anything else except the ecu. anyone have a computer they want to sell for a 99 discovery 1?

 

It's not the ECU. These trks are not that smart, they are just one step removed from a carburator.
Check your throttle cables, are they stuck? How about your butterfly, is it sticking?
Ever thought that the used stepper motor that you bought is bad?

 

check your right bank breather when its running, that might help. Its sounds like me and you have the same issue.
Post your fixwhen you figure it out. Do you have misfires by any chance?