Originally Posted by Graystroke
I would try cleaning the the throttle body flap and the IAC motor thing. Flem you said it was all one motor...does it still have a plunger like a taditional IAC? If so maybe it is dragging or the seat is gunked up? Don't have any experience on LS motors. On anything else, where I had a similar issue, it was the EGR or the IAC. the EGR can certainly cause weird idle problems and a surge if it is acting up... Leah's
bastard Honda Passport (w/ the Isuzu motor and GM engine management :rolleyes: ) started surging, pinged on the highway, would idle high sometimes and then barely idled and threw a check engine light, after a week. I pulled the codes and it was a "dealer only code" :rolleyes: according to Vatozone. I googled the code and it was an EGR code. New EGR was $185 IIRC. I pulled it and sprayed it down w/ some cancer causing Berryman carb cleaner and all has been good for over a year.
My RR always runs better after the IAC, throttle body, and PCV is cleaned out...worth a try and cheap anyways.