Land Rover Repair: Discovery Stalls when starts, land rover service, crank shaft

Question
Hi John I have a 99 Land Rover Disc 1. It just so happens when I turn on the air condition then start my car; it stalls, it idles really low then comes back up this happens *sometimes.I took it to Land Rover and they said it was a carbon build up on the throttle and the I.A.C. They said they cleaned the throttle and the idle air valve and they ran the diag test and no codes were found. The car road fine for a week and then the same problem happend... only this time it would start then turn completely off. Therefore I took it back to the Land Rover Service Center and they said they can't find the problem because it was working fine. I know I had Land Rover to replace my fuel pump last year... and the crank shaft sensor and the cat... converter. John Can you please help me!!:-)

Answer
Hi YeVonne,

Terrible when they say "there is no problem" and you know otherwise.  

From what I know about IAC valves - they are either stuck open or closed. IAC controls idle speed, so if its faulty you'll have low or high idle speeds when you start you engine.  Sounds like dealer gibberish for we'll charge you $$$ to clean this thing and when you come back, we'll charge you even more to replace it. :o

Could be IAC/Stepper motor, TPS sensor, a electrical short somewhere within the sensors, ECU is notorious for having corrosion and random shorting.  Find a local independent LR shop before LR inherits your bank account.

Best of luck,
JohnMc