When I spray carburetor cleaner on the end of the throttle shaft on my carburetor, the engine runs differently. I know the fix is to take the carburetor apart and repair it, but it is not fun to work on it in the cold. It doesn't run badly the way it is, but is there any other type of temporary fix?
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an alternative browser.
You should upgrade or use an alternative browser.
Throttle shaft leakage
- Thread starter trynew
- Start date
- Status
- Not open for further replies.
not a legal one. just leave it.
Kestas
Staff member
No temporary fix. At this point you either get a new carburator, or if it's an expensive carburator, you get the throttle shaft assembly rebushed at a shop.
A worn throttle shaft mostly affects the idle.
A worn throttle shaft mostly affects the idle.
It really only is a concern at idle and low speeds.
They are almost impossible to fix perfectly.
If they are truly horrible, you can bush the body of the carb, but it will still leak a bit.
Consider this normal and expected, at least to a degree.
Also, some of the carb cleaner that you are spraying is vaporizing, and getting into the engine via the air.
They are almost impossible to fix perfectly.
If they are truly horrible, you can bush the body of the carb, but it will still leak a bit.
Consider this normal and expected, at least to a degree.
Also, some of the carb cleaner that you are spraying is vaporizing, and getting into the engine via the air.
Originally Posted By: trynew
When I spray carburetor cleaner on the end of the throttle shaft on my carburetor, the engine runs differently. I know the fix is to take the carburetor apart and repair it, but it is not fun to work on it in the cold. It doesn't run badly the way it is, but is there any other type of temporary fix?
No easy way around that one- an ordinary carb rebuild won't alter that a bit. To fix this, you have to disassemble the throttle plates from the shaft (removed the staked screws- not easy), slide out the shaft, press out the old bushings, and press in new ones. Then on re-assembly you have to carefully re-align the throttle plates to the bores and re-stake the bolts. Carb shops that would do this used to be commonplace... I dare you to find more than a handful left in the United States, and they survive on restoration business.
The good news is that there has to be a LOT of leakage before it really becomes a problem. But it is a source of unfiltered air into the intake system.
When I spray carburetor cleaner on the end of the throttle shaft on my carburetor, the engine runs differently. I know the fix is to take the carburetor apart and repair it, but it is not fun to work on it in the cold. It doesn't run badly the way it is, but is there any other type of temporary fix?
No easy way around that one- an ordinary carb rebuild won't alter that a bit. To fix this, you have to disassemble the throttle plates from the shaft (removed the staked screws- not easy), slide out the shaft, press out the old bushings, and press in new ones. Then on re-assembly you have to carefully re-align the throttle plates to the bores and re-stake the bolts. Carb shops that would do this used to be commonplace... I dare you to find more than a handful left in the United States, and they survive on restoration business.
The good news is that there has to be a LOT of leakage before it really becomes a problem. But it is a source of unfiltered air into the intake system.
Kestas
Staff member
I've run into this problem only after the carburator has hit 150K.
Originally Posted By: severach
Engine control systems are designed to handle vacuum leaks. The PCV is the big one. A small leak in the shaft is inconsequential. When it gets large enough to allow the throttle to stick then it's time to get it serviced.
The computer is programmed to know exactly how much air a functioning PCV valve is letting in.
Also, some systems are more sensitive to vacuum leaks than others.
Engine control systems are designed to handle vacuum leaks. The PCV is the big one. A small leak in the shaft is inconsequential. When it gets large enough to allow the throttle to stick then it's time to get it serviced.
The computer is programmed to know exactly how much air a functioning PCV valve is letting in.
Also, some systems are more sensitive to vacuum leaks than others.
Kestas
Staff member
Originally Posted By: severach
Engine control systems are designed to handle vacuum leaks. The PCV is the big one. A small leak in the shaft is inconsequential. When it gets large enough to allow the throttle to stick then it's time to get it serviced.
Yet for some reason a sloppy throttle won't allow for a steady idle.
Engine control systems are designed to handle vacuum leaks. The PCV is the big one. A small leak in the shaft is inconsequential. When it gets large enough to allow the throttle to stick then it's time to get it serviced.
Yet for some reason a sloppy throttle won't allow for a steady idle.
A throttle shaft leak on a carb will affect certain cylinders more than others, and it will vary as the carb heats up.
This is not metered air that is going through the carb as it should, and causes anomalies.
This is not metered air that is going through the carb as it should, and causes anomalies.
Most engines that have carbs, dont have much for engine management. My Grand Wagoneer, uses engine vacuum powered widgits connected together with 40 feet of vacuum hose to pass emissions. If your car is old enough to have a carb, it has 20 yr old dry rotted vacuum hoses which affect the running more than a loose throttle shaft bushing.
Originally Posted By: andyd
Most engines that have carbs, dont have much for engine management. My Grand Wagoneer, uses engine vacuum powered widgits connected together with 40 feet of vacuum hose to pass emissions. If your car is old enough to have a carb, it has 20 yr old dry rotted vacuum hoses which affect the running more than a loose throttle shaft bushing.
Depends on the car....
I have worked on some GM carb engines where there were as many sensors as an EFI engine, but a carb was used. The spark was 100% computer timed.
Most engines that have carbs, dont have much for engine management. My Grand Wagoneer, uses engine vacuum powered widgits connected together with 40 feet of vacuum hose to pass emissions. If your car is old enough to have a carb, it has 20 yr old dry rotted vacuum hoses which affect the running more than a loose throttle shaft bushing.
Depends on the car....
I have worked on some GM carb engines where there were as many sensors as an EFI engine, but a carb was used. The spark was 100% computer timed.
It is an 81 Mercury Capri 2.3 (same as a Mustang). It runs fine but I can feel a little shaking when idling, especially when under load, like when it it is in drive at a stoplight.
On some carbureted cars I have had in the past, if the vacuum operated secondary barrel plate was not closing tightly, the richer mixture from that barrel would cause the engine to idle roughly. But I haven't checked that on this car yet.
On some carbureted cars I have had in the past, if the vacuum operated secondary barrel plate was not closing tightly, the richer mixture from that barrel would cause the engine to idle roughly. But I haven't checked that on this car yet.
- Status
- Not open for further replies.
Similar threads
- Replies
- 4
- Views
- 155
- Replies
- 6
- Views
- 376
- Replies
- 20
- Views
- 426
- Replies
- 82
- Views
- 2K