stuborn cranking and very slow idle

[Kudzupatch]

Now it gets Weird! Had to head to town, 12 mile round trip. Made it twice today. First trip same old issues. Once warm it idles at 625-650 RPM.

Second trip I had to go to the bank, sat in the drive through line, which I very rarely do, so it sat idling for a long time. When I left it was a little warm inside so at the red light I raised the engine speed to get the A/C working better. Turned out I turned AC off instead of hitting recirculate button. Next couple of red lights the idle speed was to high, enough you could feel it pushing as I braked. I sat there I could feel and see the RPM's slow down to normal idle.

So, obviously the IAC has decided to work. I slipped it into neutral a couple of times and it would around 1200-1500 RPMS and slowly drop back to normal. Short highway leg so I am assuming it had time to reset itself.

Got home, grabbed the laptop and took a drive and it is working normal. The IAC goes to 150 while driving and sits there. When I let off the gas is starts to drop. Now when I crank it is starts out around 1,200 RPMS as it should, then settles down. When I turn on the A/C it slows and then recovers.

Just took it for another short drive and it works perfectly. Bad connection at the computer? It is the only thing that has changed. Removed the cable and reinstalled it is all I have done.

[ChevyTech]

If every thing is good, and the system relearns the IAC position, at full operating temperature, with all accessories off, the ideal IAC count would be 20. Spec is 1 to 50.

I would clean grounds, especially the grounds at the front of the intake.
On your 1993 there should be a ground from the battery to the fender. Check it.
And always check the grounds at the back of the passenger side cylinder head.

If it were mine I would dissemble and clean the connection to the battery junction block on the fire wall.

Take a look at the system voltage while running and make sure it is not low.

[ChevyTech]

With the engine off you should open the throttle plates all the way and look down the TBI and see if it is dirty just below the throttle plates.

I use 10 inch long giant Q-tips and lacquer thinner to clean the throttle bores.

Get the bottom of the throttle plates too.

If the bores are dirty, cleaning them will lower the IAC count.

[Kudzupatch]

IAC count is 25 at the moment.

I have done all the other things not that long ago when I was chasing a lean condition. That turned out to be bad fuel injector. But I went through a laundry list of things trying to trace that down. I will give it a second look though, something could have changed.