choke issue 17057266

[Mr Hand]

Had the choke working perfectly all year. Step on the gas once it would set to high idle around 1400 rpm. Kick it down to the second step on the cam at around 900ish rpm where it would stay until the coil heated up all the way to where it would then drop down and idle at 650.

This worked like this all year including all summer when temps didn't get chilly overnight. Choke would set with one push of the gas and work as described as above.

Until now. Now when I step on the gas once to set the cold choke, it starts fine but only idles on medium idle, or second step of fast idle cam. And if I hit the gas pedal again it usually knocks the idle back to the curb idle of 650 way before it should.

Nothing was touched on the carb, no changes made other than the mixture screws out a little bit more to get a higher vacuum reading/smoother idle.

Choke coil issue? I can't see the fast idle cam with the carb on the engine and I don't want to remove if I don't have to but I know it's not on it's highest step anymore when the engine is cold and first started..

Maybe there is a simple solution to this maybe someone can point me right direction as to what to look at.
 

[Cliff Ruggles]

With the engine cooled down overnight remove the air cleaner assembly so you can see the choke, fast idle cam, choke flap, etc.  Move the accelerator and two things should happened.  The choke flap should snap tightly closed and the fast idle cam raised to it's highest position at the same moment. 

The linkage involved may simply need cleaned/lubricated so it moves freely and those two things happen.

If the choke parts are not sticking adjust the choke coil so it just closed the choke flap and raises the fast idle cam to the highest position.  You may need to go a little further if you want the choke to stay on longer.  Do start up test and make sure the choke pull-off unloads the choke to the ideal angle.  If it is defective it may not open the choke flap far enough and the fast idle speed may be too low due to an overly rich condition.

So the pull-off is an important player in correct choke operation.  They are also adjustable on the later carburetors using a Phillips screwdriver.

The fast idle speed is also adjustable, but there is no reason anything changed with that setting provided the fast idle cam is being raised to the highest position on a cold start.......Cliff

[Mr Hand]

After looking at closely to make sure nothing was binding I was still stumped as everything was good.

The problem turned out to be simple as I expected. Somehow, the fast idle cam screw had backed off almost a full turn causing it to not hit the top step on the cam. Dunno how it happened as I never touched it.

I turned it clockwise about a full turn and now it works like it did before.....fast idle, kick down to medium idle, stay there until choke coil unloads fully then kicks down to curb idle.

Thanks for the help.

[Cliff Ruggles]

Good news, I like simple fixes........

[Brett Slater]

I'm in sort of the same boat, in that my divorced choke worked well on a different Q-Jet but is giving me trouble with the one currently on the car.

I should note in I'm using an Edelbrock B4B and a spring coil like the one offered here on your site. I've had to fabricate a rod that I've had to bend and tweak to the point where it's probably too short. I'll work on that.

Nonetheless, if there's a need for lubrication, what do you suggest? Carb cleaner? I've included a link below depicting the issue.

Any help or suggestions as to what do to is appreciated. Thanks!

Brett

https://youtu.be/SCwi5WPFcZY