Hi I'm hoping that someone can help guide me in the right direction. I have an LS3 that on occasion will rev itself to 2K RPM's at idle. I've only seen it do it when the temperature exceeds 180F.

This is an LS3 Swap for an off-road vehicle so this is the way that the vacuum is routed. I don't know if it's related but I'm also seeing a little bit of oil seeping from the passenger valve cover.

 

does it have an electronic or cable throttle body? plug in a scanner if you have one and see if the throttle position sensor is say 0% when foot not on gas pedal. this happened to me and my throttle blade was not fully closing

 

Great question. It’s the old cable style throttle body and the blade closes completely when there’s no throttle pressure.

 

I swapped something on mine one time, and i afterwards the cable was a hair too short and was holding the blade open about 20%. Hopefully that's ur issue, it's an easy adjustment via the black square on the cable line, but doesn't sound like it is.

Still try and see what the ecu is seeing as far as percentage open at idle. I think u have to do a tps relearn when swapping sensors.