Fast Idling...float or other issue?

[kkemerait]

On a 78 124 Spider with a weber 32 ADFA carb I am experiencing the following problem and could use some help.

Once the car warms up (while driving), when I release the gas pedal.. the engine keeps idling very fast ... the tach is not working but I can easily put it in 2nd gear (maybe 3rd) and go smoothly from a dead stop.

This behavior does not occur when the car is cold. When cold, and I release the gas pedal..it returns to nice quiet idle.

I should add then when it get "stuck" idling fast...if I wait for maybe 45 secs to a minute or so, it will finally (most of the time) return to idle.

Is this a stuck float or something else...any help most welcome!

Thanks

[So Cal Mark]

not a float issue, but likely a linkage issue

[kkemerait]

not a float issue, but likely a linkage issue

The linkage seems fine...best I can tell...why would only act that way when warmed up?

[bradartigue]

not a float issue, but likely a linkage issue

The linkage seems fine...best I can tell...why would only act that way when warmed up?

Do you still have the fast idle device on your car? From the factory it would have had a solenoid that turned on when the car was in 3rd or 4th gear and stayed on for a few moments, keeping the the idle high. It prevented backfiring on decel. Problem is, 40 years or so later, they don't work so hot. They can be made to work, or removed. So check and see if you have an air hose running from your carb linkage to a solenoid on the firewall. The solenoid has two wires and two air hoses (one to the carb, one to the manifold). When activated it holds the throttle open.

That's the first thing to look at. The other thing is did you set the idle on this car with it hot or cold? If you set the idle cold then you found your answer; get the motor hot and reset.

Also the water choke can be screwy. If turned it will increase the idle speed when hot. You can adjust it by loosening it slightly and turning.

[kkemerait]

Of the three options, it seems that the water choke alignment marks were off, after correction things improved somewhat, however it still doesn't idle steady. After releasing the gas..it almost stalls then, slowly increases until it can idle (roughly) ... I can't seem to find a place where it idles correctly when warm but doesn't stall out when cold. Timing is 5 BTDC, Dwell at 55 or 56, new distributor, new cap, new magnacore wires, new plugs. There is no fast idle device on the carb that I can find. Any other ideas to look at?

Thanks!

not a float issue, but likely a linkage issue

The linkage seems fine...best I can tell...why would only act that way when warmed up?

Do you still have the fast idle device on your car? From the factory it would have had a solenoid that turned on when the car was in 3rd or 4th gear and stayed on for a few moments, keeping the the idle high. It prevented backfiring on decel. Problem is, 40 years or so later, they don't work so hot. They can be made to work, or removed. So check and see if you have an air hose running from your carb linkage to a solenoid on the firewall. The solenoid has two wires and two air hoses (one to the carb, one to the manifold). When activated it holds the throttle open.

That's the first thing to look at. The other thing is did you set the idle on this car with it hot or cold? If you set the idle cold then you found your answer; get the motor hot and reset.

Also the water choke can be screwy. If turned it will increase the idle speed when hot. You can adjust it by loosening it slightly and turning.

[baltobernie]

Just guessing here, but it might be a vacuum leak. These can cause the idle symptoms you describe, but I'm unsure how such a leak could occur only when warm.