Did you disconnect the battery after you adjusted it?

I have never had to adjust an IAC valve. They have always come out of the box with the pintle extended 1-1/8" or slightly less.

After you reinstall the IAC valve and reconnect the battery, you should turn the key to the 'RUN' position and leave it sit for at least 5 seconds with the engine off. Then turn the key to the 'OFF' position for at least 10 seconds before attempting to start the truck. This should reset the pintle position.

 

OK...I think I got it fixed and this WHOLE TIME IS WASN"T THE IAC VALVE. I went to pull the valve out again today to re-adjust the pintle when I noted that the throttle plate was open more than usual. This would account for my high idle last night. The long and short is this......Every time I took the TB out, and then back in to mess with the valve, I wasn't screwing in my cruise control cable to the correct tension in order for my throttle plate stay slightly open. So...the times where I had low idle, I had screwed it in to little, thus closing the throttle plate all the way and the times that I had extremely high idle, like last night in the dark, I had screwed it in too much, thus keeping the throttle plate open to far and allowing way too much air for the IAC valve to compensate. I just got done fine tuning it to 650rpms at hot idle with the simple turn of the plastic screw. Test drove it and it did perfect. Mystery solved!!!! Hopfully, this is it for this issue and I can move on to my slow leak of front differential fluid.

 

The throttle plate should be fully closed at idle... The IAC valve is responsible for idle air flow. Manually hanging the throttle open even slightly doesn't allow the IAC to do its job. There should be just a bit of slack in the cruise cable when its not in use.

If it works for you, then good, but I highly doubt that is the true cause.

 

I agree in theory, but I tried it with it closed all the way itit idled down to 300rpms and eventually died. I have been driving it around all night, parking and restarting it and it keeps a smooth consistent idle right at 650rpms with the IAC valve adjusting as necessary to keep it there. Hey, it works for me. Maybe this is just "a characteristic of my truck"...and I tested my cruise control and it stays spot on as well. I thought I read somewhere that the throttle plate should be slightly open. In any case, the problem seems fixed. I'll report back if something changes, but I feel confident the issue is resolved. I can't thank everyone enough. I'm sure I'll continue getting and hopfully giving good results from this forum.

 

I haven't fixed mine yet... but I'll certainly look at the cruise cable. I'm pretty sure my throttle plate closes all the way at idle... but I haven't looked at it in awhile.

 

hi im having the same problems with my 96 blazer and ive read and checked /repaced everything that everyone has mentioned . i noticed that you bought your iac valve from carquest and i went to website looking to buy another iac valve but to no avail . i did see a direct replacement (ac delco) at rock auto a online parts store. im just wondering if it would be like the one you got from carquest ? crmartin36@gmail.com please contact me asap im going crazy dealing with this blazer