Sticky throttle w t f

I've been messin' with cars for over 50 years and ain't never run into anything like this. I have an A roadster with a 59L flattie. The car started running like **** so I pulled the carb off and gave it a good cleaning. Didn't help a thing. After replacing a lot of parts and not getting any positive results I changed the carb (94). Car is running fine except the throttle sticks in different spots. If you give it a quick stab it idles right down.Odd thing is it only does it when the engine is running. I thought it might be the pump plunger, cause it was kinda snug in the bore, but it returns fine when it is not running. The linkage rod does not touch the firewall, the throttle shaft is loose, when it is not running you can push it down easy or hard and it always comes right back. I has two heim joints that are very free. I've replaced the return spring to no avail. It acts like there is a vacuum pulling the throttle plates open. I'm pulling whats left of my hair out. Runnin down the road at fifty and gettin' off the gas scares the snot outa ya when it don't slow down. Any ideas from any of youse smart guys? I've tried about everything except a 20# return spring. Thanx Norm

 

i had a weird one like that the other week.
it was the carpet that was hanging up.

 

****erfly sticking in the carb bore? when it gets hot?

??

 

Even when the carb is warmed up I still have a little side play in the throttle shaft. Drove it today and it seemed to work better.......... and then it stuck again, this time missing 4th gear.
the chatter up thru the shift handle made my porcelan shift knob explode. **** never ends. I'm done..... tomorrow its getting a monster return spring. just hope my ankle holds out.

 

****erfly catching on the carb gasket?

 

have you tried a stiffer spring yet? I had the same problem when I upgraded to the tri-carb set-up. Added a better spring and good as new. Hope that helps.

 

Too high float setting?

 

Exhausted all efforts, gave in and put a much larger return spring on......seems to be working alright. Still bugs me as to what is causing the problem. Thanks all for the advice. Coop

 

That sounds like a Toyota story.

But it is most likely true in one of our old hoopties. I suppose that vacuum could be holding it open but I would look for a different culprit, like the carpet or a rough spot on the strottle lingage or bell crank.

 

good thing about the spring. I hope that helped a lot. Good luck.

 

Are your motor mounts ok? I had a car that had bad mounts, when the engine shifted slightly (like when taking off from a stop) it would pull the throttle linkage and it would stick open.

 

I've had Holley 4 barrels that the choke fast idle cam would hang just enough to do that with the choke fully open.

 

Check the motor mounts!

 

X3 on the motor mounts. I had the same issue on my 63 galaxie at 60+ mph and then traffic slowed to a stop it was downright scary. then I thought to turn the key off. hahaha. things you dont think of when you panic.

 

Cool car.....

 

My throttle sticks after it's warm, a quick press on the pedal it goes away..however went wide open and stayed open today while out, I turned off motor, played with linkage and went back to sticking...and punching the pedal, making it go away... Aggravating...

 

Have seen bad motor mounts on mid year Corvettes make the linkage bind.
Back in the day moms 68 Torino GT with 302 and auto trans had the the pedal stick to the floor a few times due to a bad hose on the vacuum modulator

 

I had a similar problem not long ago with my '72 IH Travelall, high idle > stab the pedal and it goes back down. The route of the problem was the throttle return spring.

 

I had to clean up my linkage from the pedal to the carb to clear up my sticky throttle. Used wd40 and that problem was gone. Not to say I don't have other issues, but the linkage isn't one of them. You have to figure dirt and rust are going to be there when the car has set for about 20 years.