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Hello!
1995 Z-28, K&N, Borla, otherwise stock.
Distributor, wires, and plugs replaced in last 18 months.
Slowly (over a couple months) developed a higher and higher idle. Now when warm, idle will "stick" at 2K+, suddenly drop to normal, then climb back up OR SES light comes on. Codes EGR, 44, 64 (O2 sensors).
Just replaced O2 sensors, no help. Checked for air leaks, vacuum lines: no apparent leaks. Moving EGR manually affects idle (slower). Throttle butterflies are free and close.
Anyone have any ideas, I'm stumped........
Dave
 

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Most likely the idle air control valve. You can remove it, extend the pintle all the way out, clean the bejeezus out of it with intake cleaner, reset the pintle height (you'll need to find out what it should be or at least measure it before you move it), and reinstall to see if that gets you anywhere. My S10 did the same thing although it did not throw any codes. I also removed the thottle body and cleaned it out since it's only three bolts on a 4.3L. An LT1 tb should be pretty easy to remove as well.

The bad thing is that I cleaned the original and it didn't really help so I bought a cheapie IAC valve as the first thing and the issue didn't improve (actually got worse) so I spent a couple hundred bucks on everything else it might have been. I was about to redo all the intake gaskets as a last resort. I decided to really clean the original valve and tb one more time and when I pulled the new IAC valve I found it was bad....the pintle had siezed. The original is back in and working OK now.
 

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Is this a TPI?
 

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'95 Z28 so it should be an LT1.
 
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