I have a 1995 with the 4.3L. Not too long ago I drove it a little too hard when it was cold. It then began idling too low, and wanting to stall at lights. About a week later, (after driving like a grandpa for a week) the engine began idling extremely high (1400 RPM). I had a mechanic run the OBDII codes on it, and it came up with 1.) EGR Valve, 2.) Rich Exhaust, & 3.) Idle Position Sensor. I asked the lovely folks at Auto Zone what it would take to replace the Idle Pos. Sensor and they informed me that there is no such thing as an Idle Position Sensor. Instead, I replaced the Idle Air Control Valve at their suggestion. Now my vehicle idles at 2100 rpm. I can't take this much longer, can anyone help me out? Thanks in advance!

 

check the wiring to the IAC, I do know that if its unplugged it will idle that high.

 

Sounds like a vacuum leak to me

 

pull and clean the idel air control valve, check voltage to throttle position sensor, should flucuate when moving the throttle clean EGR valve
and also check the voltage to the air temp sensor located in the rubber boot to the throttle body
should be 5volts I had a wire break inside the insulation for the wire, it's not visible to the eye so check voltage, computer was reading air temp as -40F which made the truck idel around 2000 rmp

 

Just had a silmilar problem. Tried a bunch of things and the problem turned out to be a bad connection to the Throttle possition sensor. Try pulling out the sensor plug cleaning the terminals and plug it back in.

 

If it has a TBI.Under the TBI is a gasket with foil on both sides,it can suck a piece of the foil up,giving it a high idle..you can check thiswith brake clean.Spray it at the base of the TBI, If idle goes higher you found your problem....