What's this other adjustment screw on my carburetor?

toyota
pickup

#1

There’s another adjustment screw on my carburetor, a little bit to the left of the idle adjust screw, a little bit beneath it, pointed more upward, not-seeable when the air cleaner is mounted. It’s the 22 R engine.

The Chilton’s diagrams of the 8, 18, and 20 engines have ‘fast idle adjusting’, ‘mixture adjusting’, ‘throttle position adjusting’ screws, not the 22R’s diagram.


#2

Can you post a photo? I’ve had a lot of experience with 22Rs, but cannot envision your description.


Can I install a tachometer?
#3

I don’t have a camera, but after putting a stronger light on it I see that the throttle rests against it when its all the way out: it sets minimum throttle. That could have caused my problem, had it been screwed in all the way.


#4

@RandomTroll NO NEED TO START A NEW THREAD IMHOP see


#5

Can’t speak to the 22R carb, but fyi my Ford truck carb has adjustments for

  • idle air/fuel mixture (2)
  • idle rpm selonoid-off (I think this is the same as the screw you describe above, to prevent dieseling problems and prevent the butterfly valve from damaging the throttle seat area)
  • idle rpm selonoid-on ( idle rpm in normal operation, engine warm, either this one or the one above is also called “curb idle rpm”, never can remember which is which)
  • fast idle rpm (idle rpm when engine is cold and choke is enabled)
  • relationship between choke plate angle and fast idle cam.
  • relationship between choke plate angle and choke spring-thermostat temperature

#6

And what, physically, does this do? The throttle rests against mine when there’s no foot on the gas pedal: it sets a minimum.


#7

Yeah I was thinking a fast idle cold adjustment screw. Best you can do with one of those is screw it all the way out. They were a hazard in the winter on ice.
Brakes on but accelerator still spinning the rear wheels.


#8

The fast idle adjustment on my truck’s carb sets the idle rpm when the engine is cold and the choke is still operating. When it is in effect, there’s a little cam that pokes out and holds the throttle butterfly valve open a tad more than it would be for a warm engine.


#9

While I won’t guess what the screw is I did find the specification for the fast idle adjustment and believe it or not it’s 23* with the carburetor inverted and the fast idle cam on the first step according to Motors.


#10

I don’t understand what this means. 23* ?


#11

An angle gauge is commonly used to set the choke adjustment as shown in the picture, on your carburetor a gauge is also used to set the throttle angle for fast idle.


#12

Thanks @Nevada_545. Is there a degree symbol hidden on my keyboard somewhere?

And those feedback Q-jets were great when everything worked according to plans… A nightmare otherwise. Twenty-eight seconds of ticking and 55% duty cycle comes to mind. I still have a drawer dedicated to electronic carburetors and most of the tools are for E4MCs.


#13

° gets you ° in html, which works on this site.