High idle…all of the sudden!

[DeepC73]

I have a 1973 Bronco with original 302. It has a Holley 350 carburetor. I drive this thing every day. I have noticed since it is cooling off outside that the idle is a little high (idling around 700-800 rpm). Today I cranked it up and it won’t get below around 1000rpm. I have tried everything and can’t find it. The only vacuum lines on it are the distributor, the auto transmission solenoid and the valve cover which goes to the intake manifold directly. Any help is appreciated. It ran fine all week. It has a new timing chain and gears about 6 months ago.

 

[Oleguy 74]

check choke adjustment.

 

[DeepC73]

check choke adjustment.

I drove it around for 30 minutes. The choke seems to be working correctly. It was wide open when I checked it after 15 minutes of warming up.

 

[DeepC73]

check choke adjustment.

I just checked the plastic fast idle cam behind the choke. It was indeed stuck. Thank you sir!

 

[DirtDonk]

Common problem. Sometimes a reasonable and quick temporary cure is to spray it with carb cleaner, then follow up with some light lube like WD-40. Yes, we know it's not a lube, but it sure works well as one!
But you can use the thin lube of your choice as long as it's something that won't gum up in the old weather.

In fact, just the cleaning and no lubricant is probably best for a low-mileage carburetor. But once they get miles and years on them, they sometimes respond better to a good lubing.

Glad you got it fixed!

Paul