Good evening all ...

In this thread:
https://www.thirdgen.org/forums/carb...hen-start.html

Sonix says don't touch the choke pull-off. It's the screw at the pink arrow in the q-jet pict in that thread.

Well, you guessed it, I touched this screw. But not on purpose! I was looking for my fast idle screw on my stock LG4 and thought in one of the exploded Quadrajet diagrams I have that the choke pull-off screw was in fact the fast idle screw. Oops. Therefore, I changed the choke pull-off setting thinking I was adjusting fast idle. The end result is now my car doesn't go to fast idle at cold startup, instead, it just goes right to curb idle and lumps there for a bit. Once the engine is warmed up, it is fine. Is there a procedure for testing and setting the pull-off adjustment back to 'default'? I have gathered articles on fast idle, regular idle, and I see the warning not to touch the pull-off setting, but I can't find a thread on actually setting this screw.

 

Gee, I've touched that one many times. . .

With the engine shut off, manually close the choke and apply the pull-off. The pull-off should open the butterfly a crack. If it's opening the butterfly too much, turn the screw clockwise.

If your fast idle shouldn't be affected by the pull-off until you tap the throttle after the engine starts. Make sure the choke closes completely when cold and the throttle is cracked, and that the fast idle is adjusted properly.

 

Thanks! I went down tonight, popped off the air cleaner, and did as you instructed. The choke buttefly snaps fully closed when I tap the throttle linkage as expected. Once I figured out that the little vacuum can sucks the pull-off lever INTO itself, I realized how it worked. Haha. This has all been a great learning experience, just like I have my own Thirdgen Mechanic Team. Anyway, I fooled with the screw until when I pushed the rod into the canister, simulating vacuum, the choke just cracked open. It's 11:00PM here in my apartment building so I wasn't about to fire up the car. I'll let you know the results later this week. Plus I need to tweak the fast and curb idle adjustments yet. One thing I noticed is just how CHEESY that pull-off mechanism is. I mean, it's pretty easy when doing it manually to jiggle that rod in just about any direction 10-20 degrees. I guess once the vacuum comes on it just pulls it straight back ... but still, I was surprised it wasn't more, well, "solid." As for the fast idle not being affected by the choke pull off until I tap the throttle after starting up, I'm not sure. I swear that the "no fast idle when starting from cold" condition began after I monkeyed with the pull-off screw, HOWEVER I do not rule out that the fast idle is simply out of adjustment as being the major contributor. For one, you taught me it is not insane to consider that a new carb needs a little tuning, second, I'm a noob, and third, you know what you're talking about.

One more curiousity. Right near the pull-off is a little mechanical tab marked "E" on the side of the carb. It controls the choke and it appears to have three detent positions. As you push down, each detent opens the choke butterfly more and more until it is full open. Is that controlled by the electric choke mechanism? Under what conditions would each detent be used (1. a bit more than cracked, 2. partial open, 3. then full open)? Is it simply related to engine temperature to slowly allow more air and lean out the mixture ... like 1. engine stone cold, 2. engine warm, 3. engine full hot @ operating temp?

Anybody around here going to the Firebird Lawn Show in Saratoga, NY this weekend? I might be up there.

 

cam steps

fast idle cam is what that is

the steps make the throttle open more and more

fast cold idle speed

the steps get smaller as the choke opens more, to slow the engine down

until the last step in which is not touching the linkage and instead the throttle will now sit on the idle speed screw


choke pulloffs i rarely ever use on my vehicles
because i tend to not need or choose to really rev my engine when its cold

so no real need to pull the choke open when its mostly shut when its really cold

asking questons like you have bene is a good way to learn how these parts work on these carbs

i didnt learn this way but i learned by taking apart and looking at diagrams and reading repair manuals also, on adjustment procedures and so on

there are alot fo adjutments i still dont know much about and dont mess with usually

some adjustments for these carbs actually involve bending a tang or a tab

literally


keep researching and reading and you will encounter all kinds of adjustment procedures and technical terms and such



just my $.02



good job




and good luck

 

Thanks, Randy.

This morning I decided arbitrarily to take the car out since it's a damn nice day. Since my pull-off adjustments last night, the car indeed is fast idling again. Interesting. So I think I have it back to where it was before. Perhaps I had rigged the pull-off such that it pulled the choke open way too much and ruined the fast idle? I'm confused because, unless I've misinterpreted, I *think* Five7kid told me that the pull-off shouldn't affect fast idle? I just want to make sure I understand the relationship of cause and effect as I adjust things so I can understand the proper way it works.

I brought my handy screwdriver with me and later today I'll see about some small adjustments to the curb idle. On these screws, it's clockwise to increase, counterclockwise to decrease, is that right?

In other news I need to get back to trying out my dwell meter as well. Some of you gave me advice on locating the green spade connector for (+) dwell but I still have to fish around some more to find it. Perhaps one of those infamous photos with some colorful arrows will be the best way to describe what it is I'm seeing/looking for.

 

I have the same problem as necros9828. Car starts out at about 300-400RPM and will stay like that until it fully warms up. It will then go back to its normal 500RPM (well, not really normal since regular idle is about 650, but the person who rebuilt my carb set it to 500 to save on gas while idling). Im going to have to adjust the choke pull-off to see if I get fast idle again.