Originally Posted by Mike Freeman

There are several things to check before replacing the valve
#1-O.V.P. must be good. Do you have power to the valve?
#2-Is mixture too lean?
#3-Make sure idle contact in throttle body is good.
#4-Make sure Decel switch is functioning.
#5-Make sure the EGR valve is not sticking open.
#6-Check the solder joint on the Hall effect speed sensor for Cracks
There are a few devices that use TD signal from the ignition, Make sure that one of these arn't shorting to ground.
Good luck and post your fix
Mike