My 1996 Z28 has been idling too high recently. It idles at around 950 to 975 RPM, and sometimes a little higher. I thought that it was the throttle body because I had it bored to 52MM so I removed the butterflies and went around the edges to make sure that there was enough clearance. I also installed a new TPS and IAC and the TPS voltage looks good. The car is a garage baby and only has 33,000 miles on it so I can't figure out what the problem is. The car runs real well and made 300RWHP and 314 RWTQ with stock tune and less mods listed than below. Any suggestions would be helpful. Thanks.

Black 1996 Z-28, 6spd with Pro 5.0 and Lou's Short Stick and MBA ****, K&N cold air, 52MM polished TB, Granatelli Mass Air Flow sensor with polished ends. Crane valve springs, Comp hardened push rods w/guide plates, Comp Pro Magnum roller rockers. Hooker ceramic coated long tubes with mufflex Y pipe, SLP Dual/Dual Cat back with Moroso Spiral Flow bullet in Intermediate Pipe. MSD 6A, MSD coil, MSD plug wires, NGK TR55 plugs. March underdrive pulleys. Auto meter electric Fuel pressure gauge in pod and Scanmaster. Granatelli 255lph in tank pump. Aeromotive adjustable fuel pressure regulator. 6AN braided fuel lines rerouted from factory location. DMS drop springs, BMR control arms, adj. panhard rod. Spohn weld-on lower control arm relocating brackets. Enkei Win wheels with 275/40/17's in front and 315/35/17's in back. Polished aluminum radiator cover, polished aluminum valve covers, polished aluminum Vortech elbow, chrome alternator, ceramic coated intake, ceramic coated water pump housing with Mezeire Electric water pump, ceramic coated accessories bracket. Passenger side wire mod.

 

You may need to close the throttle a bit by adjusting the stop screw. Think of it this way. With the stock blades there was a gap around them that let in some, maybe tiny bit, air. IF the blade size is increased that gap surface is increased and letting in more air. Crank the screw back a bit and see what happens. The IAC should do the work. There was an excellent post on the adjustment providing of course you can scan to adjust. In any case crank er back.

 

Thanks for the reply, I have adjusted the throttle stop to where it is nearly all the way back, I thought that would take car of it also, but it didn't,

 

Anybody else have any input?