Stepper motor acting crazy.

I recently drove my 96 Disco I 3000 miles from Seattle to Arkansas. While in the Arizona desert, 200 miles from anywhere, my vehicle speed sensor went out. It scared me pretty badly when it started to stall, but then I noticed the speedometer going nuts, and realized that I could just unplug the sensor and drive to safety in open loop mode. That worked great with one exception. My Idle speed was a little faster every time I would stop for gas. After driving 1200 miles with the VSS unplugged, I finally reached my destination, promptly sourced a VSS, and installed it. The new sensor works great, but to my dismay, the Idle speed is still around 3000 RPM. The stepper motor is functioning, but not correctly. It starts at normal speed, but within 8 seconds it slowly opens up to 3000RPM. When the engine is shut off, the stepper motor closes again. I read on the rave cd that a failed VSS will do this, but I had hoped it would clear up with the new VSS. Do I need to have the stepper motor recalibrated? No vacuum leaks. The only codes are P0446 and P0451. Also the O2 sensor heater monitor, and the Evaporative control monitor will not run there tests. They do not seem to be related, but did appear at the same time as the idle problem. Please help. I would like to have some kind of clue before I go to the shop.

Thanks in advance.

Regards
Thad G.

Hi Thad,
I have a 96 Disco. I had this same idle problem and replaced the stepper motor to no avail. I found out the hard way in that in part of 1996 Land Rover used a different alarm system. Make sure you know a very good Mechanic who really knows his stuff! It turns out even Land ROver in England didn't have much info on this alarm. To make matters worse my ECU had corrosion inside of it so bad that when you shook it up and down in your hand you could actually hear the rice krispies inside. So I ended up with a uesd ECU-my mechanic treated me supurb on a price- a used alarm ecu and he finally managed to get the two to work together with his software. I have the car back and it runs fine. Make sure you still have at least one of your alarm remotes too and that it's working.
I hope you do not have this problem with yours and that it's simple but since you have a 96 and i just went through this, I thought I'd drop you a note.
Basil

About 2 months ago I also had the same problem as Basil with my ECU. My Mechanic also made me a great deal on a used ECU. Problem is, when they reset the adaption for my truck, they never erased the adaption for the old truck it came out of. They also did not change VIN numbers in the ECU. When the Speed sensor went out, the ECU defaulted to the adaption for the old truck. I found a land rover specialist here in North Little Rock Who was able to switch my ECU VIN to match my trucks VIN, erased the old adaption and let the ECU re adapt to my truck. It took him 15 minutes to get my truck in, find the problem, fix it, and send me on my way. He only charged $40. I was Happy!