I’m trying to figure out what this part is on my carburetor that seems to be keeping the idle really high. Here’s a link to the picture
Any help or advice would be great. I’m new to working on my own truck but trying to learn.
Thanks for posting your question! If possible, include details like the year, make, model, mileage, engine size, and transmission type so everyone can help you better. This forum is here to help, so feel free to share more info!
That’s a dashpot. It cushions the throttle when it closes and helps keep the engine from stalling. The electrical part bumps up the idle when the AC compressor is on. Your idle adjustment is that long bolt near the red arrow. High idle could be from a vacuum leak—check hoses, caps, and the brake booster. Also, if you’re worried about oil pressure, use a mechanical gauge for accuracy.
It’s an idle stop and dashpot. The dashpot prevents the throttle from slamming shut, which could pull in too much fuel. The idle stop solenoid (or throttle kicker solenoid) keeps the idle stable. Check for vacuum leaks, especially the brake booster and hoses.
If this system is causing too much trouble, some people swap out the carb for a more basic one like the Motorcraft 2150.
@Sage
That’s definitely the way to go if you’re tired of dealing with all the extra stuff.
@Sage
Thanks for the detailed reply! It does seem like it might be a vacuum issue. I’ll start checking hoses and the booster. This truck has been giving me some headaches, but I’m determined to get it running right.
@Presley
Good luck! A lot of newer mechanics don’t know these older systems well, so it’s great that you’re digging into it yourself.
Looks like someone’s been messing with it. The solenoid with the cut wire should keep the idle stable until the ignition is turned off. That long screw is for adjusting the hot idle speed. The diaphragm is a dashpot to prevent the engine from dying when the throttle slams shut.
@Kingsley
Totally cobbled together. I sold this truck to my cousin, who is a duct-tape mechanic, and it came back to me like this. Thanks for pointing me in the right direction!
That’s your fast idle solenoid for when the AC is on. If the AC and defrost are off, it shouldn’t hold the throttle open. Check for vacuum leaks—look at the PCV valve, vacuum hoses, caps, and the brake booster. Spray carb cleaner around the carb base gasket and intake gaskets to find leaks. Let us know what you find!
@Chris
Thanks! Every time I hit the throttle, it sounds like a turbo hissing, so I’m sure there’s a vacuum problem. No AC installed, so I’ll dig into the other suggestions and report back.
Presley said:
@Chris
Thanks! Every time I hit the throttle, it sounds like a turbo hissing, so I’m sure there’s a vacuum problem. No AC installed, so I’ll dig into the other suggestions and report back.
Sounds like a plan! Post more pictures if you want help spotting the issue.
That’s an electric choke.
There’s an adjustment bolt on that part. Try turning it to lower the idle.
Looks like an electric choke that’s been modified. Try adjusting the bolt closest to the camera to see if it helps. The cut wire should be connected somewhere, but you’ll need to check where it originally went.
@Sam
That’s what I was planning to do first. Thanks for the advice. Should I consider removing it and going to a manual choke?
Presley said:
@Sam
That’s what I was planning to do first. Thanks for the advice. Should I consider removing it and going to a manual choke?
You could, especially if the smog systems are already defeated. It might simplify things.
Judging by that bolt in the vacuum line, you’ve probably got some vacuum leaks or dry-rotted hoses. Replace those before messing with carb tuning.