If hitting the pedal drops the idle speed back to normal, the choke is open. Is this happening after the engine is warmed up? If so, check for binding in the linkage or at the carb. I once had a wire harness bundle move into a position where it would occasionally cause the throttle to hang up. I've also had a throttle body-to-main body gasket that stuck out into the throttle bore just enough to hang up the throttle blades. And if you have a cable throttle, the braided cable starts to wear with age and bind in the sheath. There are a lot of possible causes unrelated to the choke.
Too fast idle. Electric choke problem or false air?
My engine have started to not go back to normal idle.
Don't happen all the time, but often.
If I hit the gas pedal, it (usually) goes down to normal idle.
Feels like the choke doesn't goes off, but I'm not sure.
CSB 350, QFT (Holley) 670 cfm carb with electric choke.
I suspect either false air or electric chocke malfunction?
Don't have any reason to suspect false air. Everything sit tight.
Don't happen all the time, but often.
If I hit the gas pedal, it (usually) goes down to normal idle.
Feels like the choke doesn't goes off, but I'm not sure.
CSB 350, QFT (Holley) 670 cfm carb with electric choke.
I suspect either false air or electric chocke malfunction?
Don't have any reason to suspect false air. Everything sit tight.
1 - 12 of 12 Posts
If you take the air cleaner off before you start it you can see the position of the choke and linkage...
Also back when I was very young I had a similar problem but it would not hang up the choke unless the air cleaner was on due to the fact that when the wing nut was tightened on the air cleaner it would squeeze the sides of the carburetor just enough to bind up the choke...
Also back when I was very young I had a similar problem but it would not hang up the choke unless the air cleaner was on due to the fact that when the wing nut was tightened on the air cleaner it would squeeze the sides of the carburetor just enough to bind up the choke...
The action of the choke valve and the fast idle cam are semi independent in that when the thermostatic control is cold then acting as a spring it loads the choke valve but the the choke valve and fast idle cam remains where it last was till the throttle is opened then the thermostatic spring pressure closes the choke and pulls the fast idle cam up on the fast idle step which can be several sequential steps that proportion idle speed to choke valve position.
The fast idle cam although pulled up by the choke’s thermostatic spring is not forced downward by it as the choke valve is opened, that function is a small counter weight built into the shape of the fast idle cam. This is the weak link in the function of these things as functionally it’s hinge mounting and attached linkage all cannot develop more resistance to movement than the small amount of force induced by the counter weight can or the fast idle cam will not fall from the fast idle position. A little physical damage, corrosion or dirt accumulation anywhere in that system, also, miss adjustment or one that doesn’t hold of the fast idle screw will result in the cam staying in the fast idle position without regard to what position the choke valve is in.
Bogie
The fast idle cam although pulled up by the choke’s thermostatic spring is not forced downward by it as the choke valve is opened, that function is a small counter weight built into the shape of the fast idle cam. This is the weak link in the function of these things as functionally it’s hinge mounting and attached linkage all cannot develop more resistance to movement than the small amount of force induced by the counter weight can or the fast idle cam will not fall from the fast idle position. A little physical damage, corrosion or dirt accumulation anywhere in that system, also, miss adjustment or one that doesn’t hold of the fast idle screw will result in the cam staying in the fast idle position without regard to what position the choke valve is in.
Bogie
Thanks for your answers, friends!
Guess it’s time to dig into the choke function and increase my skills!
Guess it’s time to dig into the choke function and increase my skills!
Also take a close look at the linkage movement as you slowly move the throttle back and forth with the engine off. For example, sometimes the fast idle cam will stick on high when you slowly drop the throttle, but if you quickly drop the throttle the vibration/shock will make it pivot and work properly.
Check choke position with engine hot. Should be open fully. Base gasket or vac leaks on a carb won't cause fast idle. That is only on throttle body injection. Ernie.Also take a close look at the linkage movement as you slowly move the throttle back and forth with the engine off. For example, sometimes the fast idle cam will stick on high when you slowly drop the throttle, but if you quickly drop the throttle the vibration/shock will make it pivot and work properly.
Once you look inside the choke this will make much more sense.
Some chokes have a round rod on the linkage. The choke spring has a round hole that this rod is meant to sit inside. If you put the round part before this it can cause the choke to stay closer longer. Usually there is enough adjustment to "fix" this easy to make mistake but not always. It has been years since I played with a Holley electric choke carb. I dont know if the choke pulls or pushes. If it pulls and is not attached to the rod it is not going to be able to adjust the butterfly.
Fast idle cams and solenoids(mostly factory) can open a whole new world of fun so check inside the choke first.
Some chokes have a round rod on the linkage. The choke spring has a round hole that this rod is meant to sit inside. If you put the round part before this it can cause the choke to stay closer longer. Usually there is enough adjustment to "fix" this easy to make mistake but not always. It has been years since I played with a Holley electric choke carb. I dont know if the choke pulls or pushes. If it pulls and is not attached to the rod it is not going to be able to adjust the butterfly.
Fast idle cams and solenoids(mostly factory) can open a whole new world of fun so check inside the choke first.
Another thing that can happen with electric chokes on the Holley carbs that I have encountered was a similar situation but not as bad was where even after my choke was fully open and you hit the gas to take it off fast idle is it would let off but my idle was still a few hundred rpm higher then what it should be and where I had my idle setup at.
Example is my fast idle was around 1500 rpm and then after it was warmed up I would hit the throttle and it would drop down to about 1000 rpm when my idle was setup for around an 800 rpm idle. I could see where choke was open and the fast idle arm was all the way down but yet my idle was up 200 rpm too high. I had no binding on the linkage that I could see and at times I could get my idle down to 800 if I pressed on the throttle shaft.
I looked over things and tried to see what the problem was. I eventually found out that if you have the fast idle speed screw in so far to give a certain higher rpm that on the first ramp to have the high idle that when it lets off and the choke coil is full heated and the choke flap is open and you hit the throttle it will release the fast idle ramp bracket and it will go down to the last setting on the ramp and the fast idle screw should not make contact with it but if its setup high enough then when you let off the fast idle then the linkage will fall to the down position but it will contact the fast idle screw just a hair and will hold the idle slightly higher.
When I set mine up I set it for a high enough setting and then hold my choke flap open and open the throttle up and let the fast idle linkage go all the way down and then I hold the carb upside down and look at the fast idle screw and make sure its not making contact with the fast idle linkage at the lowest position. After I found this little problem out I dropped my fast idle just a hair and then make sure there was clearance for the fast idle screw and the linkage on the bottom most setting and I no longer had my idle being slightly higher then what I set it at with the choke off.
Example is my fast idle was around 1500 rpm and then after it was warmed up I would hit the throttle and it would drop down to about 1000 rpm when my idle was setup for around an 800 rpm idle. I could see where choke was open and the fast idle arm was all the way down but yet my idle was up 200 rpm too high. I had no binding on the linkage that I could see and at times I could get my idle down to 800 if I pressed on the throttle shaft.
I looked over things and tried to see what the problem was. I eventually found out that if you have the fast idle speed screw in so far to give a certain higher rpm that on the first ramp to have the high idle that when it lets off and the choke coil is full heated and the choke flap is open and you hit the throttle it will release the fast idle ramp bracket and it will go down to the last setting on the ramp and the fast idle screw should not make contact with it but if its setup high enough then when you let off the fast idle then the linkage will fall to the down position but it will contact the fast idle screw just a hair and will hold the idle slightly higher.
When I set mine up I set it for a high enough setting and then hold my choke flap open and open the throttle up and let the fast idle linkage go all the way down and then I hold the carb upside down and look at the fast idle screw and make sure its not making contact with the fast idle linkage at the lowest position. After I found this little problem out I dropped my fast idle just a hair and then make sure there was clearance for the fast idle screw and the linkage on the bottom most setting and I no longer had my idle being slightly higher then what I set it at with the choke off.
Sounds very familiar.....Another thing that can happen with electric chokes on the Holley carbs that I have encountered was a similar situation but not as bad was where even after my choke was fully open and you hit the gas to take it off fast idle is it would let off but my idle was still a few hundred rpm higher then what it should be and where I had my idle setup at.
Will for sure check this out as well!
When I twist the choke cap to set the choke (nearly) closed, the alignment mark on the black plastic cap is way outside the scale it should be within.
See photo with arrows.
I have disassembled the black cap to check it. The spring looks fine. Not loose.
(Yes the choke is slightly too open on the photo, but that's not the point right now).
The choke linkage moves freely and nice.
What do you advise?
Should I replace the cap and spring?
![]()
See photo with arrows.
I have disassembled the black cap to check it. The spring looks fine. Not loose.
(Yes the choke is slightly too open on the photo, but that's not the point right now).
The choke linkage moves freely and nice.
What do you advise?
Should I replace the cap and spring?
Rotate the cap all the way lean.
crack open the throttle slightly.
rotate the cap cw until the choke blade just closes.
tighten the screws.
done deal.
that’s your best lean setting.
crack open the throttle slightly.
rotate the cap cw until the choke blade just closes.
tighten the screws.
done deal.
that’s your best lean setting.
1 - 12 of 12 Posts
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