Diagnostic Aids

An EGR valve pintle constantly in the closed position could cause detonation and high NOX emissions. It could also result in high long term fuel trim values in the open throttle cell, but not in the closed throttle cell. An EGR valve pintle constantly in the open position would cause a rough idle. A EGR valve mounted incorrectly (rotated 180°) could cause a rough idle. Check EGR passages for restricted or blocked EGR passages. Check MAP sensor. If MAP sensor calibration that has shifted will affect fuel delivery.