Okay, I am going to try and explain my problem as throughly as possible. First off I have a 1997 Land Rover Discovery. My idle speed is very high! When I turn the vehicle on the idle speed will shoot up to around 2500 RPMs. This started happening this morning after I plugged a cord into one of the components on what I believe to be the throttle body. Before this incident I had similar problem with the idle being too high, but it was only around 1500 RPMs, still driveable in my book. After the vehicle was started it would idle aorund 1000 RPMs and after it was hot it would go up to around 1500 RPMs. Other aspects of the problem that might help isolate the issue of high idle speed are 1. When you plug the cord into the component, the vehicle wants to limp at first and then shoots up to 2500 RPMs after the engine turns over. 2. When you unplug the cord the vehicle doesn't want to turn over at all, but after a few turns of the ignition it will finally turn over and shoot up to 2500 RPMs. 3. After about a half an hour of tinkering with this component I got it to run at the previous idle of 1000 RPMs, which is still high compared to the 700 which is spec. 4. Currently the cord is unplugged from the component and I am driving without the cord connected.
I have been doing some research into the issue and have come acrossed some information that links this particular issue to the TPS sensor, but have not been able to locate the sensor in my manual and also, believe that the disconnected cord from the unidentified component and TPS sensor may be two seperate problems.

 

here is a larger expanded picture of the area of interest, that might better help you understand what we are looking at.

 

Idle Air Control Valve or IACV. It is a 200 position stepper motor that finely adjusts the idle speed by computer controlled vacuum leak.

To service, remove , but DO NOT ADUST TIP. Spray with carb cleaner to remove gunk. Also clean the bore it mounts in. If there are other vacuum leaks, you will have additional problems.

If your ECT (Engine Coolant Temeprature) sensor is acting up, it can also make high idle as computer thinks the truck is parked at Santa's Workshop at the North Pole, and needs more gas. Might just be unplugged, it is the one with a square plug near the thermostat. Can be evaluated by scanner, if coolant temp shows really low (like -40), then sesnor is not working. Note that this is a separate sensor from the heat gauge (single wire on lthe left in pix below).

 

I brought a brand new one from eBay for $20 shipped. It the same part for a Jeep.

 

The TPS is right next to it, in your picture. Right behind the disconnect connector.

Have you yet tried disconnecting your TPS?

I had a similar problem when the cam of the throttle body, un-clocked, from the TPS cam. You can instantly tell if you disconnect it.

 

So I determined that one factor that was causing the high idle was the hose next to the IACV unit was torn on the underside and causing the release of vacuum pressure from the plenum housing. I replaced the hose and now my idle is much more consistent to the spec 700 rpms. Although the stepper motor is still giving me some grief... When I plug the unit into the ecu it still wants to shoot up to 2500 rpms. Is this related to a bad IACV unit or is the due to a seperate issue?

 

Did you figure out your idle issue? I am having a similar issue, I bought two new Stepper motors and a TPS sensor. Does the computer have to "learn" the new components? My idle is around 2500rpm with the newest stepper, and an occasional 1500rpm with the other new stepper.

 

I hate when people spend money because there mis informed.. Ok not bragging but I think I'm the master with this. I had the same problem various times..

Chances are your oll TPS was good, the computer just forgot what base closed was. Unfortunately you HAVE to have adaptive values reset. Usually 1hr shop charge. Don't even bother trying anything else. Trust me I tried it all.. You drive without the TPS plugged In and then plugged it in.. Have to have it reset sorry

 

Bummer, this happened after I cleaned the throttle body and I never drove it while unplugged. I have another Q, is the MAF sensor supposed to face the engine so it says Lucas upside down?

 

That may ow mine started/ I wish this was more known. Do not for any reason remove TPS or unplug it unless its already broke.. That's my take on it...

And the maf rotation doesn't matter as long as the direction is correct. I don't think it's possible to put on backwards so your good