1996 Landcruiser idle too low

Hello all,

We had the headgasket replaced a couple of weeks ago and since then the vehicle has not idled well at all. It will stall when driven if you just let off the gas and even the cold (high) idle is only about 800 RPM. The dealership that replaced the headgasket (it was leaking coolant internally) has replaced the Oxygen sensors and the catalytic converters (didn't understand that one) in an effort to fix the idle. All along they have claimed that the coolant being burned messed up the Oxygen sensor (I can believe that one) and the cats. Well the engine runs fine above idle and has plenty of power all the way up to the redline. So I think it is an idle air control valve or something with the computer.

Any help or advice is greatly appreciated.

TIA

Joe

P.S. I don't know why the headgasket went out and haven't heard of anyone else having to replace one on that motor.