High Idle 84 chevy C20 w/350

[gill finn]

Hello all, my truck starts without issue and is at normal high idle, however it won't drop back down. It remains stuck until I put it in gear of course, but as soon as it's put in neutral/park, it quickly returns to its high spot. I don't know a lot about its history, I just bought the truck and I'm in the process of changing fluids, bleeding brakes (they go to the floor) etc. But, I'd like to get this idle issue tended to, thanks for any input, much appreciated.

 

[Krausmotorsport]

Hey Gill!, I'm new here myself but not new to forums or the SQBDY life. You either have a carb issue or vacuum issue. Check your vacuum ports. If it was a 87 trouble shooting would be slightly different with it being EFI

 

[Originalthor]

I agree with krausmotorsport check for vacuum leaks. Right off the bat.

Did you try kicking it down sometimes a choke can be sticky and need a good kick down to release it.

On your carburetor on the passenger side is your choke. Some are electric and some are ran by heat from the intake. Once its warm pop the air cleaner off see were the top flap is. It may need adjustment or not working at all.

If the choke is working correctly then I would check timing and then your idle adjustment screw.

Few more details would be nice too. Or couple pictures of your carb if you choke is not working to help fix it.

 

[PrairieDrifter]

I would say choke is improperly adjusted. If not open far enough the fast idle won't kick down.

 

[Finkaire]

Mine did the same thing, there is an adjustment for the high idle. I adjusted mine down to where I don’t think I have a choke any more. I have to feather the throttle to keep it running in the morning but then it runs fine, just passed smog. I have the electric carburetor

 

[gill finn]

Wow, thanks for the help everyone! The exterior of the carb is pretty dirty, so I'll give that a good cleaning, also yes, I thought vacuum leaks could be an issue, I've ordered some in bulk and I'll go around and replace them all. I'll get back to this thread when I'm finished and let you all know what's up. Again, thank you for the info! I've also picked up some vacuum tube so I'll begin changing those out as well. These are more general engine bay shots I took prior to cleaning the carb, I'll get some closer tomorrow.

 

[gill finn]

Hello again, well I've cleaned all around the exterior of the carb, it's looking good, I'll get some photos later. The idle seems a bit better, but all the gauges are not operating, that's annoying, also headlights as well. Tail lights do work, the turn signal cluster seems to be not working either. I have checked the fuses and they all seem to be okay. Slow going.

 

[Originalthor]

Sorry I missed this. I got my notifications turned off. It looks pretty clean there. Choke looks pretty newish or you did a real good job of cleaning it. Its is electrical so with the key one check to see if its got 12 volts.

Your other stuff and possibly it not running right could be grounds. Clean them all. Theres 2 on the core support, 2 on fire wall , 1 on the back of the head usually passenger side, and a junction box above the emergency brake pedal in the cab. And probably one I'm missing.