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high engine idle,vortec 5.7
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vehicle is new to me .98' k1500 started to develop a high idle,and a miss. codes where misfire #5,and the iac.i cleaned the throttle body replaced the iac.it was still idling high 2,900 rpm. in gear 1,300 rpm.it was getn worse had to stop driving.so i tore into it doing a intake manifold gaskets.old ones where plastic .i cleaned the fuel poppets and manifolds good .it runs better but i have the high idle. when i first start it fires rite up and goes to2,000 rpm. i will floor the gas and after it will idle down and run fine.but when i restart it does the same thing until i floor it.can anyone help i have check connections and hoses .not where else to turn to except by another iac. thanks everyone!

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Have heard somewhere the brake booster may leak internally pull the hose and plug it with your thumb and see if it idles down. Hope it works ...Lorne

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I wonder if the egr valve could cause somewhat of a vacuum leak also? The break booster and the check valve sound like a great place to start.
When I changed to the 0411 ecm and unplugged my IAC valve to check wire colors and forgot about it, It appeared plugged in by looking at it until I physically pulled on it. Hopefully its something simple.
Good Luck
Robby

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Spay some starting fluid around the intake, you'll find the leak real soon.

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i'm sure its not a leak.i just replaced the tps sensor ,code threw at me.still a high idle.what is weird is that one day it started to run fine .idle rite where it was to be .and most of the time it doesn't go down untill i floor it! then when i go to restart it back again. i have heard off resetting the pintle on the iac. anyone heard of this? any ideas before i take it in?

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smittyred1 wrote:
i'm sure its not a leak.i just replaced the tps sensor ,code threw at me.still a high idle.what is weird is that one day it started to run fine .idle rite where it was to be .and most of the time it doesn't go down untill i floor it! then when i go to restart it back again. i have heard off resetting the pintle on the iac. anyone heard of this? any ideas before i take it in?


If working properly, I believe the IAC resets itself every time the key is turned off, that way it has the starting position
by driving the pintle all the way in and then backing it out to a preset # of counts that way it knows where its location is
during start up.

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