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can't get idle down AFTER re-activating choke:

vandelay industries

vandelay industries

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First let me apologize (for NOT adopting current technology---because i'm cheap and have chosen to continue to live in the past) and to ask help from 21st century inhabitants:


i can't get the idle down to normal in drive since i reactivated the choke. (new quadrajet)


1) i had wired the choke AND fast-idle cam completely open last summer, because i needed the truck running asap and didn't have time to mess with this back then. And it ran great with idle in neutral around 800-900 and in gear 500-600rpm.

2) After reactivating the choke (because it got cold) i can't get the curb idle down to normal---which is 500-600 rpm in drive. Now it's 700-800rpm in gear which isn't bad but it's not optimal.

a) The choke IS opening normally.
b) Hi step, hi mid step are definitely functioning normally. Not sure about low mid step, although the fast idle cam DOES appear to be moving to it's last position each time the choke opens fully.
c) i have the curb idle screw all the way out to the point that the throttle arm is barely touching it, if at all.
d) i did turn the fast idle screw out quite a bit to some improvement, but this shouldn't affect curb idle which makes me think something isn't right here......
Before i backed out the fast idle screw, curb idle was about 900 rpm in gear.

Just curious for your general thoughts on this and what i might be looking for? i have not ruled out the possibility of a vacuum leak, but do not feel strongly about it because what are the chances i could have gained a vacuum leak EXACTLY when i reactivated the choke?

i have also not ruled out the possibility of either a sticky vacuum advance or centrifugal advance, but again what are the chances this could have happened at EXACTLY the same time i reactivated the choke?
 
I'd say first two things to check if the choke fast idle cam is in fact going back to the lowest step after warming up,would be a carb base gasket that's letting air sneak in,(a vacuum leak,also check all the vacuum hoses,PVC valve,brake booster ,trans modulator if you have one)--or the secondary butterflies might be sticking open a bit,not closing fully can raise the idle speed a lot...
 
It should stay on the high idle cam until the choke is open and then you move the throttle. You should be able to watch it work when moving the throttle by hand (or see what isn't). Sometimes they just need carb cleaner and lube.
 
Ok, as it turns out, the choke lever and thus fast idle cam WERE NOT going down all the way----it stayed on the very last step of the fast idle cam apparently;

It APPEARED as if they both went down all the way, but upon further inspection they did not. (even though the choke plate itself DID open up all the way)

What i then did, on a whim, was to re-wire the choke lever and fast idle cam all the way down with a ziptie and turn the choke coil fully open, as i had it last summer. And idle returned to normal----900-1000 in neutral and 500-600 in gear.


So, i've identified the problem; The choke plate DOES open fully vertical after about 2 minutes, but the fast idle cam does not go further than the last step.

But i don't know where/how/what to adjust?
 
Yeah, if it is a hot air style choke, look for a break in the stove pipe in the intake manifold that feeds the thermostatic coil in the choke housing. Look at the choke housing where the coil is, does it have rivets holding the cover on, or are there screws there so you can take the cover off and get to the coil to adjust it? What are the numbers on the carb ?
 
I have the same truck. My choke linkage was stuck, just sprayed the linkage liberally with carb cleaner to free up. I don't think you are supposed to lube with anything cause it will attract dirt and make it stick again. The thermostatic coil might be bad, or simply need to be adjusted.
 
There also could be something bent somewhere in the choke linkage. Hope you get it fixed . Let us know what you find.
 
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