Location of idle screw on a engine

a pickup , hardbody means pickup bed walls are double walled, only. aka D21 pickup?
USA car, " ? not told engine there, lots of engine world wide, but ours is but 1. USA>
2.4L? Iine 4 cylinder.
guess #1 real name of real engine by them..
2.4 L KA24E I4 (1990-1997)
in the USA the EPA banned all those screws.
by law. the idle speed is fully computer controlled.
all USA cars, idle speed is regulator fast by the PCM
using device called IAC/ISC/ has 2 wire IAC.
IAC is bolted to TB lower side base, 2 wires.

if Idle hot is not at 800RPM and not regulating there are 3 common causes.

1. ISC is stuck (needs cleaning)
2. vacuum leaks, makes the ISC useless. (over-ranged) cracked vacuum lines and more.
3. thermostat bad,engine never gets to 180f up. temp.

the screw here is factor OEM calibration
called the never touch screw.

yellow circled. this screw sets idle duty cycle to 50%
as covered in the real service manual
seem carb guys monkey this screw and IAC and PCM go nuts.
if was messed with by others I set mine to
0.001" gap TV to bore inside the TB bore'/

On some float-type carburetors, you can adjust the air-fuel mixture and engine speed at idle. Check for an idle speed screw designed to keep the throttle plate from closing completely, and an idle mixture screw that limits the flow of fuel at idle. If your carburetor contains these screws, proceed below.

1. With the engine off, remove the air filter and air cartridge.
2. Locate the idle mixture screw and turn it clockwise until the needle lightly touches the seat. Then, turn the screw counterclockwise 1-1/2 turns.
3. If your carburetor has a main jet adjustment screw at the base of the float bowl, turn the screw clockwise until you feel it just touch the seat inside the emulsion tube. Then, turn the screw counterclockwise 1 to 1-1/2 turns. Replace the air cleaner assembly and start the engine for final carburetor adjustments.
4. Run the engine for five minutes at half throttle to bring it to its operating temperature. Then, turn the idle mixture screw slowly clockwise until the engine begins to slow. Turn the screw in the opposite direction until the engine again begins to slow . Finally, turn the screw back to the midpoint.
5. Using a tachometer to gauge engine speed , set the idle speed screw to bring the engine to 1750 RPM for aluminum-cylinder engine or 1200 RPM for engine with a cast-iron cylinder sleeve.
6. With the engine running at idle , hold the throttle lever against the idle speed screw to bring the engine speed to "true idle." Then, repeat the idle mixture screw adjustments from Step 4 to fine-tune the mixture .

Three screws. On some, there are only two screws. Some have only one screw. A few have none at all.

If there are any screws, one is nearly guaranteed to be an idle mix adjustment. With the engine warmed up & idling, turn that screw in (clockwise) 1/4 turn at a time until you can hear the idle speed drop a little. Back it out 1/4 turn and leave it alone. If the first 1/4 turn drops the idle speed, turn it OUT 1/4 turn and see if the idle speed rises more. When you get idle speed that stays the same when you make a 1/4-turn adjustment, go back to the beginning if this paragraph and repeat the first part.

If there are two or three screws, the next screw may be either an idle speed screw or a high mix screw. If it's an idle speed screw, turning it in 1/4 turn will immediately RAISE the idle speed and turning it out will LOWER the idle speed. Adjust that screw until the string head (that cuts weeds) isn't quite turning at engine idle. If it's a high mix screw, its only effect will be at full engine speed. If the engine sounds throaty, turn that screw in 1/4 turn at a time at full engine speed At some magical point, the engine sound should turn brassy. If you turn the screw in past that point, the engine will lose power because it's running too lean.

If there are three screws, then you have all three - idle mix, idle speed, and high mix.

There may be markings near the screws to identify them. Each manufacturer marks them differently, if at all. Some manufacturers simply rely on the screws' locations to indicate what they do. It'll be up to you to figure out which is which and make notes accordingly.

There is no idle adjustment screw, as idle is controlled by the car's computer through the idle air control valve (IAC). This is possibly sticky, and needs a clean. There is a throttle stop screw on the engine, but that is a different thing.

There is no idle adjustment screw on this engine, which is normal for EFI engines. The idle is controlled by the car's computer. It does this by controlling the Idle Air Control - IAC - valve, which should be checked in your case. See here p271

http://www.turboninjas.com/camry/eg2.pdf


There is a throttle stop screw, not the same, on the throttle body, which you may be thinking of, p263. This does not directly control idle speed.


Also the A/C, if any, can affect the idle if the A/C idle-up switch has failed. If testing this switch, do so when the engine is hot, as that is when they fail. See p295

Hi allenplum,
There are 2 mixture screws, 1) the idle speed screw, 2) is the idle speed mixture screw. The idle speed screw is located on the carburetor, nar the throttle arm where your throttle cable is connected. There is a screw that you will find there that you screw in or out to speed up, or slow down the engine idle. The idle speed mixture screw is located lower down on carb and has a spring on it. There should be 2 screws side by side, one is the idle speed and the other is the high speed mixture screw. They are marked on the carb body, with the letter H or L . To adjust, remember the screw position before you do any adjustments. Start by turning the screw in (clockwise) all the way in until lightly seated, so no damage is done to the seat or needle. Turn out (counterclockwise) 11/4 inch, this should be OK to start the engine. Along with the idle speed screw, you should be able to get the correct idle required. With all the modernization happening, there might not be a high or low adjust as they are ported inside the carb. You might get just the high or just the low adjust needles. I hope this is helpful to you. All the best and good luck. Denis.

mcdevito75 here, The fast idle is needed when the engine is cold to make the air and fuel mixture rich to keep the engine running while cold, the carb. choke doew this with a bi-metalic spring in that balck round box on the side of the carb, a screw also hepls keep the choke closed until warm up, this screw can be adjusted tpo control how tight it holds the choke cloesed, here"s how to adjust this screw to slow fast idle speed, Locate on the carb, where the gas pedal connects, have a friend operate the gas pedal with the engine off, once you locate the linkage, you"ll also see 2 screws with springs around them, 1 is for fast idle the other for regular idle, you want the fast idle screw, notice this screw will lay against and Half moon shaped tab, while the other screw lays against a shaft, you need the screw that lays against the half moon shaped tab. Start the engine and step on the gas pedal slightly and relaease, at the screw that lays against this half moon, simply turn it counter clockwise or toward you just 1 2 or 3 turns very slowly, you'll hear the fast idle come down but you don"t want the fast idle to low, listen to the engine very carefully, slow it down just a bit, it should still race though but not out of control. Of course for a full carb, adjustment the shop should handle that., but this info will help.

On any carburator,one screw is for the idle speed, the other the air/fuel mix.Start the engine and let it get plenty warmed up. Adjust the idle screw to make the engine run slow. Turn the air/fuel screw in until the engine starts to die then out till it starts running loady.You want the screw between these two locations. Adjust it till the engine runs the fastest. Now adjust the idle speed screw to about 1000 RPM.
I hope this helps you.

ADJUSTING THE IDLE SPEED AND MIXTURE
On some float-type carburetors, you can adjust the air-fuel mixture and engine speed at idle. Check for an idle speed screw designed to keep the throttle plate from closing completely, and an idle mixture screw that limits the flow of fuel at idle. If your carburetor contains these screws, proceed below.

1. With the engine off, remove the air filter and air cartridge.
   
2. Locate the idle mixture screw and turn it clockwise until the needle lightly touches the seat. Then, turn the screw counterclockwise 1-1/2 turns.
3. If your carburetor has a main jet adjustment screw at the base of the float bowl, turn the screw clockwise until you feel it just touch the seat inside the emulsion tube. Then, turn the screw counterclockwise 1 to 1-1/2 turns. Replace the air cleaner assembly and start the engine for final carburetor adjustments.
   
4. Run the engine for five minutes at half throttle to bring it to its operating temperature. Then, turn the idle mixture screw slowly clockwise until the engine begins to slow. Turn the screw in the opposite direction until the engine again begins to slow (image A). Finally, turn the screw back to the midpoint.
   
5. Using a tachometer to gauge engine speed (image B), set the idle speed screw to bring the engine to 1750 RPM for aluminum-cylinder engine or 1200 RPM for engine with a cast-iron cylinder sleeve.
   
6. With the engine running at idle (image D), hold the throttle lever against the idle speed screw to bring the engine speed to "true idle." Then, repeat the idle mixture screw adjustments from Step 4 to fine-tune the mixture (image C).
   

Hello

>>The Following is an Instruction File I made for Correcting this Problem. Any Input is Appreciated.
>>****All the Carburetor Adjustments are the Same for Lawn Mower and Trimmers.
>>There are Several Location for the Air Mixture Screws.
>>The Idle Air Mixture Screws are Usually Located at the Top of the Carburetor Bowl and the Top of the Carburetor Body.
>>If the Main Air and Idle Air Mixture Screws are Side by Side on the Side of the Carburetor, then the Idle Air is the Nearest to the Engine.
>>The Main Jet Air Mixture Screw is Located in the Bottom of the Carburetor Bowl or Beside the Idle Air Screw on the Side of the Carburetor Body.
>>The Engine Idle Screw is Usually Easy to Identify because you can See where it Makes Contact with the Carburetor Throttle Shaft Plate Stop Ear. The H and L Air Mixture Screws Go Into the Body of the Carburetor and the Tips Cannot be Seen.
>>Some of the Older Model Carburetors have the Main Jet Mixture Screw Straight in from the Top of the Carburetor Body (this is Rare anymore).
>>If you have Cleaned the Carburetor (Disassembled and Soaked Overnight in Carburetor Cleaner (I Use Gunk). Then Blow Out the Passages with Compressed Air and Install a New Kit if Required.
>>Now Setting the Air Mixture Screws:
>>****Turn the Idle Air and Main Air Mixture Screws In Until SNUG **Do Not Jam** Then Reverse Both Screws 1 1/2 Turns.****
>>Holding the Throttle Full Open, Start the Engine.
>>Turn the Main Air Mixture Screw Clockwise Until Proper Revs are Obtained. Occasionally you May have to Turn this Counter Clockwise to Achieve the Proper Revs. Now Allow the Engine to Idle.
>>Set the Engine Idle Screw (Not Idle Air) so the Engine will Stay Running if Required.
>>Now Set the Idle Air Mixture Screw so there is No Hesitation when Throttling from Idle to Full Throttle.
>>Reset the Engine Idle if Required. If This Carburetor has a Single Air Adjustment.
>>Use the Section Above that Pertains to Full Throttle RPM Air Mixture Screw and then Adjust the Screw if Required to Eliminate Any Hesitation when Rapidly Throttling from Idle to Full Throttle.**
>>1- http://www.repairfaq.org/samnew/lmfaq/lmclctc.htm
>>2- http://www.cpdonline.com/692509.pdf .
Please, Do Not Hesitate, If you Hit a Snag or this Does Not Correct the Problem, I am Here if You Require More Assistance.
Hope this Helps. Let me Know What Happens, Please. May the All Mighty Bless You and Yours. Be Safe and Be Happy. Thanks.

Good Luck

Respectfully

jbridger (John)