Diagnostic Aids
WARNING: This page is about a different car, the 2002 Isuzu Trooper, 2002 Isuzu Rodeo Sport, 2002 Isuzu Rodeo, 2002 Isuzu Axiom, and 2002 Honda Passport. However, it is still accessible from the selected car via links, so may be relevant.
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.