Anyone have problems with carburetor throttle getting stuck on Chrysler 400 engine?

Fred A

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Has anyone experience carburetor throttle getting stuck on Chrysler 400 engine? Fix?
 
Which carburetor? What vehicle? Did this just start or has it been progressing for a while? Is the throttle cable sticking or the fast idle cam not falling down when the engine warms up?

CBODY67
 
I once had a kick down linkage twist over a long period and was catching on the valve cover and rubbing in the firewall real low so it wasn’t t seen immediately. Mine stuck wide open throttle one day.
 
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My secondaries stuck wide open on the butterflies at the intake manifold. It was due to the gasket.
 
Which carburetor? What vehicle? Did this just start or has it been progressing for a while? Is the throttle cable sticking or the fast idle cam not falling down when the engine warms up?

CBODY67
Fast idle not falling down when engine warms up
 
Fast idle not falling down when engine warms up
That could be the vacuum pull-off or the choke thermostat isn't adjusted right. Is the exhaust crossover blocked? That can cause the choke thermostat to not get hot enough.
 
Not sure. Here is the situation I adjusted the carburetor in garage and everything is idling smooth. I drive it outside half way out of driveway and stop..The car is idling real fast. I have to manual adust the idle screw to get it back down. You think the carburetor needs to be rebuilt? The car has been parked in garage for many years.
 
My secondaries stuck wide open on the butterflies at the intake manifold. It was due to the gasket.
Perhpas there is a message there?

Under normal situations, the base gasket is enough bigger than the carb throttle plates to have ample clearance in that area. No reasom for the base gasket to change over time from just sitting. Ideally, no carburetor should suddenly need a rebuild after sitting, even for years. BUT as the fuel in the carburetor might evaporate, sometimes some residue is left behind which might cause the throttle plate shafts to resist coming back to hot base idle position as easily as before.

You might, with the engine off, manually fully open the throttle and spray a quality carb cleaner into each venturi to wash off any possible residue. Moving the throttle as you do. Then let everything sit for a day or so before starting the car again. Letting all of the vapors from the cleaner evaporate out.

Also spray down the throttle linkage on the carburetor, too. Ensuring the choke butterfly is free-working, too.

If the vacuum pull-off has failed, there should be a vacuum leak combined with the fast idle not coming off initially, which can result in a 1500rpm fast idle speed.

I'm suspecting the heat riser passage under the carburetor is still open? Even so, it can become caked-up with carbon, which can keep the choke thermostat from heating up as it should.

For good measure, do get a wrench and snug-down the carb baseplate nuts to ensure they are all tight.

Please advise of your progress,
CBODY67
 
Not sure. Here is the situation I adjusted the carburetor in garage and everything is idling smooth. I drive it outside half way out of driveway and stop..The car is idling real fast. I have to manual adust the idle screw to get it back down. You think the carburetor needs to be rebuilt? The car has been parked in garage for many years.
If it's been parked for a lot of years, it would be a good idea to get it rebuilt. Gaskets dry out or shrink and they can leak.

I don't think that's necessarily your problem though... Could be the vacuum pull off or the choke not adjust correctly.
 
Perhpas there is a message there?

Under normal situations, the base gasket is enough bigger than the carb throttle plates to have ample clearance in that area. No reasom for the base gasket to change over time from just sitting. Ideally, no carburetor should suddenly need a rebuild after sitting, even for years. BUT as the fuel in the carburetor might evaporate, sometimes some residue is left behind which might cause the throttle plate shafts to resist coming back to hot base idle position as easily as before.

You might, with the engine off, manually fully open the throttle and spray a quality carb cleaner into each venturi to wash off any possible residue. Moving the throttle as you do. Then let everything sit for a day or so before starting the car again. Letting all of the vapors from the cleaner evaporate out.

Also spray down the throttle linkage on the carburetor, too. Ensuring the choke butterfly is free-working, too.

If the vacuum pull-off has failed, there should be a vacuum leak combined with the fast idle not coming off initially, which can result in a 1500rpm fast idle speed.

I'm suspecting the heat riser passage under the carburetor is still open? Even so, it can become caked-up with carbon, which can keep the choke thermostat from heating up as it should.

For good measure, do get a wrench and snug-down the carb baseplate nuts to ensure they are all tight.

Please advise of your progress,
CBODY67
Thanks for your input, but this was years ago. Back then I tried everything you mentioned except for the vacuum pull-off. All the bolts were tight. When this happened, I shut off the engine and looked at the secondary butterfly valves at the bottom of the carb. They were always getting stuck, either partially of completely wide open. I had to pull them shut.

It could have been the shafts. I never thought about that. I sprayed them well, but never removed them. Since I still had the lean burn carb, I got a rebuilt 1975 non-lean burn thermoquad and it's been wonderful ever since.
Afterwards, I had to replace the front pads and rotors because I used the brakes to stop the car the first few times this happened. I still have the original drums and asbestos shoes at 52k.
 
If it's been parked for a lot of years, it would be a good idea to get it rebuilt. Gaskets dry out or shrink and they can leak.

I don't think that's necessarily your problem though... Could be the vacuum pull off or the choke not adjust correctly.
I went to start it yesterday and see fuel leaking down the manifold. Think it is coming from the carburetor gasket? Fuel line seems ok
 
I went to start it yesterday and see fuel leaking down the manifold. Think it is coming from the carburetor gasket? Fuel line seems ok
It kind of depends on where it's leaking. IMHO, it wouldn't hurt to have the carb rebuilt. As said, gaskets shrink etc., especially with the ethanol laced fuel.

I'll suggest sending it to Woodruff carbs. @Dana is a member here and he does some great work. Carburetor Restoration in Youngstown, OH | Woodruff Carburetor Specialties
 
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