A stall at idle may be caused by a malfunctioning IAC valve. Use the WDS VDR or Data Logger
and record: B+, RPM, IAC, MAF and TP and duplicate the concern. At idle, when IAC duty cycle
is commanded high or low, the MAF signal will follow the IAC command if the IAC valve is
functioning normally. An abnormally functioning IAC valve will result in an IAC command with
very little or no change in MAF signal. The following graphs explain :

· Normal IAC valve operation
· Abnormal (sticking) IAC operation