2000 Chevy Silverado High Idle Problem

BecauseAmerica1 · February 13, 2022

This is my last resort, I’ve searched all over the internet. My 2000 Silverado with the 5.3 has a high idle problem, it idles at 1000 rpm constantly. It only idles normally when my ac compressor is actively running. I have replaced everything, intake gaskets, idle air control valve, throttle position sensor, MAF. Have tried to find vacuum leaks but they aren’t any. If anyone has ever had this problem please help me solve the issue. I’d really prefer not to have my ac compressor turned on because my evap core drain is clogged and it leaks into my floor on the passenger side.

CamGTP · February 13, 2022

If you unhook the throttle cable does it still have a high idle?

If it does then it has to be a vacuum leak or the throttle blade screw needs adjustment. Typically the blade adjustment is a last resort type thing.

A vacuum leak would also show very high fuel trims too on a live data scan tool.

BecauseAmerica1 · February 13, 2022

32 minutes ago, CamGTP said:

If you unhook the throttle cable does it still have a high idle?

If it does then it has to be a vacuum leak or the throttle blade screw needs adjustment. Typically the blade adjustment is a last resort type thing.

A vacuum leak would also show very high fuel trims too on a live data scan tool.

Unhooked the throttle cable and the cruise control cable. Still idles high. When I start the truck is idles down the idles right back up

CamGTP · February 13, 2022

What brand of IAC did you install, just curious?

Are you able to watch fuel trims on a scanner too?

BecauseAmerica1 · February 13, 2022

34 minutes ago, CamGTP said:

What brand of IAC did you install, just curious?

Are you able to watch fuel trims on a scanner too?

It was a Duralast gold IAC, two of them because I assumed I might have gotten a faulty part the first time. I do not have a live data scanner but when I do get ahold of one what should I be looking for?

also I’m very tempted to turn that idle screw one turn. There is 1 thread of shiny above the threads where it looks like it might’ve been turned before I bought the truck, maybe the previous owner turned trying to compensate for the bad iac?

Edited February 13, 2022 by BecauseAmerica1

CamGTP · February 13, 2022

You'd be looking at the long term fuel trims, if they were stuck up around 16% there would be a vacuum leak. But if the leak was that bad to cause the idle to be higher then it would already be spitting codes for a lean problem.

I'd try slowly turning the idle screw to see where that gets you. A warm idle should be around 550 rpm but anywhere close to that is fine so long as it doesn't stall at idle or when coming back down to idle.