i have a 1998 explorer with the SOHC 4.0. sometimes if i lock the wheel the engines RPMs drop soo much that the car shuts off. i was making a u-turn and it shut off. does anyone know why this is.

 

The power steering puts a load on the engine that the IAC is supposed to over come by increasing the RPM. Check your IAC to see that it is not plugged up w/debris and that it moves freely. I am sure that some other things can cause this but that is the easiest to check and the most probable

 

Does it stall when turning the wheel and sitting still or only when moving and turning(making u-turn etc)? Do you have any other idle/performance concerns(hesitations, low power etc)?

 

at idle too. if i just lock the wheel, sometimes it dies.

 

I know on our 97and up F150's there is a pressure sensor that compensates for the PS and it's not the IAC. Not sure of the proper name, I'll try to find it later.

 

Alot of EFI systems have a pressure switch on the powersteering pump or box that tells the computer that the steering is being moved , so at idle the computer will boost the engine speed via the IAC.

A faulty switch or a dirty IAC could be the problem, but you said it was dieing at lock.. Could this be a faulty pressure relief valve in the steering box? When you are at lock it isnt relieving the pressure and causing the pump to kill the engine..

I have never seen that happen but I guess it is possible..

Good luck with your problem..