I have a 2007 Trailblazer SS, 6.0L LS2. I changed the cam and valve train. Changed to a FAST LSXRT truck manifold. I noticed the throttle body butterfly is not closed all the way before starting. When started it revs to 2800 rpm and slowly comes down to 850 RPM's. When driving the truck it's at a high rev until forcing it to slow with the brakes.
Is the butterfly supposed to be open about 3/16" when the truck is cold and not running? Why is it at a high idle when starting? Any help would be greatly appreciated. Thanks
You might have to use a scanner and use the RELEARN program as you had changed out some items.
the throttle should be a little open. That's how your engine gets air for idling, because there is no separate idle valve. The dirtier the throttle body is, the wider it will open.
Engines always idle high when started because they are in open loop program. Once they warm up, idle drop to around 700-800 RPM.
