Alright boys i have another one. my 65 bonny has a carter 4 brrl. my idle is crazy high. i’m trying to lower it but it doesnt seem to have a straight forward idle screw. ive attached what it has. two small screws left/right with one bit in center and there’s another one way under the throttle linkage when you pull it back. the two little ones have to do with air/fuel and the one in the middle i believe if you screw it in, it lets in less air to carb. rather than go into all the things i’ve tried…. how would you go about lowering the idle so i have that nice slow muscle car idle? thank you in advance! top pick is one way under throttle linkage.
UPDATE: Now when i put it in park, the idle goes thru the roof and when turned off it “runs on” really bad.
Yep. The one that operates the throttle. The only thing I would add is if it has that fuel shut off solenoid or not to prevent dieseling. Don’t know when they quit. At any rate, they liked to turn the mixture screws way lean and then turn the idle screw up so it would run. Then when you shut the car off, the solenoid would de energize to close the throttle more. They’d have limiter caps on the mixture screws so yo had to keep them leaned out (until you broke them off). So if someone screwed with one and not the other, or if the solenoid stuck, you could have a screaming idle.
The big screw in the center controls the idle on Pontiacs version of the Carter AFB. Turn.it clockwise to reduce idle. Make sure when you do it that the choke is fully open and the fast idle screw is not on the cam.
If your car suddenly started idling high, it’s probably not an adjustment problem. More likely a jammed linkage or problem with the choke mechanism. First thing I would do is spray the linkage with carb cleaner and cycle it to loosen it up. I’d next check the choke mechanism. Then I’d watch several videos on how to adjust your carb.
High idle could mean a few different things, is this something that just started, or slowly kept getting higher and higher?? How high is “crazy high”?? 1000 rpms, 2000 rpms or 3000 rpms, or 800 rpms?? And does it change from cold start up to fully warmed up, does it idle normal once warmed up???
You could easily have a vacuum leak, carb base gasket, one of many vacuum hoses, intake manifold or even the carb itself…
Had a buddy installed a fresh rebuild he bought off a performance website that idled at about 3000 rpms and he traced it to the throttle blade shafts being very loose in the throttle shaft bores of the carb body, when rebuilt they didn’t bushing the shaft bores, he swapped it out for something else and it idled normal…
And no one touched anything?
Well, it was parked in barn and not driven for 7yrs?
I changed my alum intake and found out every intake bolt was loose.
Hmm, a new intake gasket and proper torque fixed it.
i did adjust it turning it to the right until just before it started making that sucking sound and it seemes a little better. but when i drove it, once fully warmed it seems really high again and if u put it in park it goes thru the roof! and now it deisels really bad
it seems to have gotten worse as weather changed. it was recently adjusted. it starts ok, just a little high. i dont have an rpm gauge so i cant say actuall RPMs. once fully hot its very fast and when put into park once hot its thru the roof. deisels bad when hot. . i will say that the gasket between carb and air cleaner is kinda stretched out so its possible its not quite sealing. i have almost no carb experience.
Once warmed up and high idling, put your hand over the top of the carb like you are trying to stop the air flow, see if it kills the engine or just lowers the rpms…
As Texases mentioned, your linkage for fast idle cam (choke on) could be sticking not letting the idle drop as it should…
This is a carburetor so a vacuum leak will not cause a high idle like it does on FI cars. First thing to check is the choke pull off. It is vacuum operated and if the diaphragm rots, as they do eventually, the linkage will be stuck on the high idle cam all the time.
Second possibility, not as common is the needle and seat are leaking, overfilling the fuel bowl and allowing fuel to spill into the manifold. When this happens, you usually get a lot of black smoke because it is running way too rich. I’ve only actually seen this once.
Edit: in @Tester’s diagram, it is called the “choke vacuum diaphragm”.
That will make no difference, mixture and idle speed are usually adjusted with the air cleaner housing off the carburetor.
On some air cleaner housing designs, if replaced in the wrong position, the housing can keep the throttle open.
