Possible causes

– Faulty Variable Intake Motor
– Variable Intake Motor harness is open or shorted
– Variable Intake Motor circuit poor electrical connection

P1159 KIA Description

Variable Intake System (VIS) is used to increase torque at lower rpm and increase horsepower at higher rpm. Sigma 3.5? engine has two intake runners for each cylinder. The primary intake runner is a long, thin tube in which the intake air passes through. This allows a strong stream of air to blast into the cylinder, helping low-end torque. The secondary intake runner is a short, fat tube. This allows a large volume of air to be sucked into the engine, increasing high-end horsepower. At lower rpm range, the engine does not provide enough suction into the cylinders, starving the engine of much needed oxygen. The skinny tube helps blast the air into the cylinder for more oxygen. At higher rpm, the engine has plenty of suction but the intake runner is too small to provide the oxygen it needs.