1500 RPM IDle

[ccso503]

Ive got a 87 TBI Blazer with everything stock. Only mods to the system is new exhaust tubing and lack of cat converters.

I idle around 1500 rpm and havent a clue on how to get it down. When put into gear, it of course drops to around 500 rpm and sound normal.

Where do I go from here?

 

[Mike D]

Check for vacuum leaks and cracked vacuum lines. The throttle body to intake gaskets were thin and notorious for leaking. Possibly when you removed the cat, the now lower restriction allowed free-er engine breathing thus faster idle. Near the throttle linkage on the TBI is an idle adjustment screw. There may be a plug over the hole where the screw is located. Remove it, use small torx screwdriver to adjust. There is a proceedure to correctly adjust the idle, I think it goes like - Key on engine off for 60 seconds, then unplug the idle air control ( IAC ), start engine adjust idle to 700 - 800 RPM, turn off engine replug IAC restart engine, verify acceptable idle. Turn off engine. The Throttle possition sensor ( TPS ) should be checked with a digital volt meter. The correct voltage should be between 0.45 - 0.55 volts key on engine off. I hope other CK5 members chime in to make sure I did't forget something. Good luck.

 

[Thunder]

As said above check for vaccum leaks. They will usually cause a high idle.
No cat convertor usually will have no effect on idle speed
Also make sure the heater control is not in Defrost if you have AC. Defrost will cycle the AC compressor and the ECM will bump up the idle speed a little to compensate for the extra drag.

The method to set minimun idle stated in above post is not quite right.
Here's how to do it:http://s-series.org/component/option,com_tech_article/Itemid,/item,63/task,item/