I don't know where the air/fuel mixture screw is on my carb

How to Adjust Fuel and Air Mixture On A Carburetor By ...

? 5:54
https://www.youtube.com/watch?v=39Wcbp6_yNQ
Feb 23, 2014 - Uploaded by TheWhatisright Hopcorvetteman
It is a standard 350 Chevy with no real modification. .... missing something or can they be in a different location on my carb ( 81vette rochester quadrojet ). ... There are two fuel mixture adjustments on the rochester Carburetor.

Start with the idle needle screw first, the idle mixture screw. Seat it all the way in, first-don't overtighten and damage it, just seat it lightly, and back out two full turns. Run the engine and set the adjustment by ear to get your best lean idle: start turning the screw in (clockwise) 1/8 or 1/4 turn at a time till engine stumbles, dies, or runs rough. Keep the engine running, and turn screw out (counterclockwise) a little at a time till you hear the idle dropping. Now between those two settings is your best lean idle. Turn the screw in, a little at a time and wait for engine to respond, tiill you get the highest idle speed. Now set the other idle screw, curb idle, to the idle setting for your truck, probably about 700 rpm. You can move back and forth between the screws to get the best steady idle. Just don't over do it on the idle mixture screw.
Good luck.

Do you have a Holly on that ? if not then, you have to pull the carb. apart to adjust the fuel/air mix, are you talking about the idle air mix screws, this only adjust the idle mix, not the fuel ratio when running above idle, I have seen slots (screw driver) oval, hex screws, your going to have to see which one you have, take the air cleaner off and reach it from the front of the van.

you wont and you cant ,doesnt have a choke ,its computer controlled fuel injection

Here are some images that might help to assist you, and let me know if you require any further assistance.


Adjust the curb idle with the engine warmed up and the choke off.




The air/fuel mixture screws should be adjusted with the engine warmed up and at normal idle speed, then turn each air/fuel mixture screw in one at a time until the engine just begins to mis-fire, then back the air/fuel mixture screw out 1-1/2 to 2 turns out a half a turn at a time until the engine idle is the smoothest. (your vehicle might have restrictor caps over the air/fuel mixture screws to limit the amount of adjustment)






The choke adjustments;






To adjust the vacuum tension pull on the choke pull-off:





Adjust the fast idle screw to the proper RPM with the engine cold and the choke on.

You need to adjust the automatic choke. Your choke may not be opening fully. There is a fast idle cam linked to the choke to keep the throttle open more until the engine is warm. The idle mixture screw is part 37 in the picture, but get the choke adjusted right first, and you may not have to adjust the mixture screw. See adjustment procedures at link beloe.



Repair Guides Carbureted Fuel System Carburetor AutoZone com

many of the late model cars & trucks can't be
adjusted some of the carbs are preset some you can force and some don't have an adjusting screw for the jets if the carb is in good working order but needs a bit more fuel you u must adjust the float for more or less fuel check to make sure the float valve is clean free and not sticking ..

In the late 70's they mandated that the adjustment screws be capped over. If they haven't been exposed, there will be two plugs covering them on the baseplate. Air adjustment screws are always somewhere on the base of all carbs with the only exception being on Holley 4bbl carbs used on performance engines (definitely not yours)

Carb.basic setting.
On the Carb to Intake manifold there is an AIR/FUEL volume control screw. Gently screw it in Clockwise until it bottoms out, then back it out 2 turns.
Next, find the Throttle Butterfly Fast/ Slow idling screw, and back it out until the Throttle linkage is released.
Then slowly wind it back in 2 turns
If you have SPARK and FUEL up, then it should Fire Up.
When it does, using the Air/Fuel screw to stabilise the idle mixture, adjust the Idling Speed Screw to run balanced at around 750 RPM.
Happiness!!!
All the best and Regards, DT

Yes, Colorado is much higher in altitude. Do to higher altitude the barometric pressure is less than sea level by a long shot. Lower barometric pressure mean that less air is entering your engine. Which in turns mean that your engine is now running richer than it was at a a lower altitude. So I recommend checking you engine timing, and adjusting your carbs air/fuel mixture. yes this means that you may need to rejet. but first there is a screw on your 22r's carb that you must adjust to lean the air mixture just right. I have had a stock 22r carbortor before and never had to rejet it. i probibly should have but it ran fine at sea level and all the way to about 10000 ft. after 10000 feet i had to lean the fuel mixture to even alow the engine to run. This screw that you must turn is hidden due to toyota not wanting you to tamper with it and burn your engine to the ground by running your engine to lean. it has a metal plug on the passenger side of the carb about the size of a pencil eraser. you must drill that out and then you can adjust the air fuel mixture. Clock wise is to lean the air fuel. and Counter clock wise is to richen the air fuel mixture.A good rule of thumb is to turn the air/fuel screw all the way clock wise and then back out about 2 and 1/2 turns. That is the factory adjustment. you may only need 2 turns out. Best of luck i hope you get it running perfect. Try this adjustment first then if it still runs rich then think about rejetting.

Here is a picture of what i am talking about.

#1 is the air/fuel mixture, #2 and #3 are cold and warm idle screws.
#4 is a A/c idle adjustment.