I have a 96 Discovery. Today I noticed that my idle has crept up on me. It use to idle around 650-700 rpms. Today it is around 1-1200 rpm. It bad enough that on a flat surface I can take my foot off the gas and the truck will slowly accelerate up to around 20-25 mph. When I come to a stop the idle goes to 1000 rpm but if I sit still long enough it will sometimes drop to 750. Is there something that would cause it to be fine yesterday and then today be acting up?

Thanks,
Jason

 

Make sure you dont have a any unplugged vacuum lines then,

Clean your throttle body and stepper motor.

Also check the throttle cable by having someone rev the motor above idle and watch to see if the cable, spring, and everything attached to the throttle body retracts to the "closed" position. also spray some wd-40 on the out side of the throttle body to lube the stuff pictured below.



*** I experienced this on a 97 and after everything I mentioned above, I had to adjust the throttle cable because it was at a setting where letting go of the gas pedal wouldn't allow the throttle body to close all the way.***

Do everything I said and in that order.

 

I will try these things. Can you try to post the picture again. I cant see it.

Thanks,
Jason

 

http://picasaweb.google.com/jycsalas...98868950751010

 

Clean your t/body and the IAC along with the hole the IAC fits into.

 

Update
I cleaned my t-body, the stepper valve, and hole it came from. Seemed to help a little. Here is whats currently happening. If I am in park or neutral the my idle is at 1K. In reverse or drive with the brake applied it will drop down around 800 (a little above the first line below the 1k line). In park or neutral after I rev the engine the idle will drop to 1k then in about 4 seconds it will drop down to 800-850 range. It would do this over and over again. Can you test the stepper valve? Also, how do you know if your check engine lights work? If they come on for the second during startup is this enough to consider the warning light are functioning properly?

Jason

 

What you are describing is exactly how my truck idles. That is how it has always been. Not sure if that is how it is supposed to be but this with a very very clean upper engine (after a head gasket job).

 

If all was normal, the factory idle should be 650 to 700 RPMs. Something is still wrong with your truck.