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1992 Chevy K1500, weird problem

I am having a weird issue with my vehicle. It will run fine and then start to idle really low (500 rpm) and if I don’t give it gas it will die. After this happens, the vehicle won’t start for awhile. It sounds like the starter won’t engage, but if I let it sit (sometimes as little as 5 minutes, sometimes overnight) it will start right up. I’m not even sure where to start looking for the issue. I recently replaced the Idle Air Control valve thinking that it might help. Any thoughts?
It has the 350 5.7L engine.

Did you clean the entire throttle body, especially the IAC port?

It sounds like you have more than one problem there. Either that, or it is all caused by the same thing, an electrical problem. Since that would be easier to test & fix, maybe start there. Have your battery and charging system tested. What does your battery voltage measure before first start of the day? And then after the engine has been started and idled for a few minutes?

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Maybe we are talking the start up and idle circuit here? I’d suspect the EGR valve first since it’s easy to check. The diaphragm might be punctured or it might be carboned up, happens all the time. Also pull out the PCV valve, and shake it. If it doesn’t click the ball is gummed up so change that out. That’s a place to start at least. That, or maybe you have a valve lifter or two that are gummed up and stuck half open (assuming yu have hydraulic lifters). If mechanical lifters they might need an adjustment, or perhaps a valve or two is sticking.

When it starts idling low, shake the IAC wiring at the connector. Have found lots of bad IAC connectors through the years.

Thanks for the replies everyone. I bit the bullet and took it into a shop. They diagnosed two separate issues. Like most of you suggested, the started needs to be replaced. The low idle/dying problem is coming from bad fuel injectors. Thanks again for the replies.

Glad you got a proper diagnosis. Sounds like the fix is in the works. Good to know. Best of luck.