84 Chevy K10 idling high

[71cuda1990]

So I have this problem I can't figure out. Got a 1984 K10 with a 305, Quadrajet, auto, 4x4. It's rusty and a project but it runs fantastic and the 4 wheel drive works awesome. Just recently though it started acting up. When it warms up the idle runs really high, almost like the choke is fully open but it's not I checked to make sure it wasn't sticking. I tried blipping the throttle like when you set the choke, nothing. I put full length headers and dual exhaust on so it has none of the original emissions junk on it, but that was before the winter and it has run fine all winter. I also rebuilt the carb around the same time. The only recent thing was a month or so ago I replaced the starter. Then today after work I was tinkering with it before I went inside and I manually opened the vaccuum secondaries, tada the idle went down to normal. But as soon as I released the secondaries it ran back up to really high. This is starting to get irritating and when it's slick out it makes driving a little hairy. This weekend I'm going to try basic maintenance stuff, plugs, seafoam, and some other stuff. Any input from the more learned guys on here would be awesome. Thanks ya'll.

 

[67Dart273]

Hard---to----say

My first guess is gummy, sticky, or bent choke/ fast idle cam linkage.

Can you tell, when it's idling high, if the throttle lever is hitting the idle speed screw? This is over on the driver side.

If you look at them carefully, engine off, you can work out how the choke linkage works and how it pushes up the fast idle cam. There's also a link in there that locks out the secondaries until the choke opens. That stuff is pretty much all on the passenger side.

 

[rmchrgr]

Sounds like a vacuum leak. When you open the throttle blade, the condition disappears because the engine is ingesting the correct fuel/air mix for the position of the throttle blades and it overcomes the amount of air the leak is letting in. Check top end mating surfaces. You had the carb off, check the gasket underneath, stuff like that. Intake manifold gaskets leak all the time especially when they get old. Check your vacuum hose connections and check the ends for cracks, make sure they're routed to the right place etc. Spray carb cleaner/solvent around all these places while the engine is running (cautiously!), see if the idle changes. If/when it does, you've found a leak source. Might be more than one so be thorough.

 

[Revhendo]

Um, 84? Electronic Quadrajet? Idle mixture solenoid?