car guys what does this adjust

[raggie33]

i usaly can fix cars with book but i cant find the book on the 92 geo prizim it uses a toyotoa corolqaa motor it has 4 cylinders and 16 valves. this screw dont efect how far the throlte plate can close. for some reason i think it adjust the air bypass at idle?
i took pic and cirlcled screw

 

[raggie33]

its a multiport fuel injected car by the way

 

[LukeK]

I don't know much about cars at all so take this with a grain of salt. Perhaps it's the screw for adjusting the speed of the motor (rpms) when idling. I know my friend's old civic has a screw kinda like that, that adjusts the idling speed.

 

[raggie33]

new pic

 

[snakebite]

it could be a throttle stop but most efi cars employ a computer controled air bleed or a solinoid to control idle.
even a haynes or clymer manual should tell you what if anything it is.

 

[Saaby]

What about a 92 Toyota Corolla book raggie, since you yourself even said they're the same car.

 

[raggie33]

thought about that saabyy but i didnt see that book either
snakebite i now think the throtle stop is what i circled in this new photo.man people who usedto own this car adjusted stuff at random lol

 

[darkzero]

Looks to me like the idle adjust. Screwing it in will lower the idle. Backing out will of course raise the idle. If the idle starts jumping up and down as if there were a vacuum leak, you have backed it out too far. Make sure the car is warm and you have the headlights on when adjusting the idle. If that's the screw, you guessed it on the dot, "i think it adjust the air bypass at idle?" Most FI Jap cars don't adjust idle speed by opening and closing the throttle plate. As snakebite said, it's controlled by an idle air control valve and bypass adj. screw.

 

[darkzero]

Raggie, keep in mind that the throttle stop screw should not be used to adjust idle. An easy way to check the throttle stop screw is open the throttle all the way and let it go rapidly. If it's backed out to far the plate will kind of get stuck as you'll notice when trying to open it again. You'll notice this in the mornings or when the engine is cold; you have to put some good pressure on the gas pedal to get the TB plate to open. If it's screwed in too far the TB plate will be open when completely off the throttle. You want the throttle stop screw just past the point where it just starts to make contact.

 

[raggie33]

it was like id say almost a 1/8 th inch away from stop screw and there is another set screw on bottom i think that moves a tad when ac is on to keep it from idleing down after the extra loud of ac is on. it never hits either of em and at first it idled around 1900 rpm lol. cold hot always was high i dont have a tach but i can tell. it stunk . it alos was kinda do to vacum leaks but i fixed most of them next step is im going to replaced the fuel injecter seals and other gaskets on intake and throtle body

 

[Dmax]

If you have high idle speed all the time it could be one of the sensors malfunctioning. Like coolant temperature sensor or throtle position sensor. You might want to get a Chilton's repair manual or an equivalent book and use a voltmeter to check that the output of the sensors is within specified range.