Idle adjust screw

[joyluck614]

My ride is a toyota corona silver edition with a 5k carburetor, medyo mababa masyado ang idling ko with makes the car vibrate too much, ask ko lang kung may nakakaalam kung saan ko makikita ang idle adjust screw sa carb ko and anong direction ko dapat iikot para tumaas ng kaunti idling ko.

Pag nakatayo ako sa passenger side ng engine, may nakikita akong color gold na screw sa ilalaim ng air filter cover sa side ng valve cover na aboout 45 degrees un angle, un po ba ang idle adjust screw? Thanks po uli mga tsikoteers!

[duskylim]

My ride is a toyota corona silver edition with a 5k carburetor, medyo mababa masyado ang idling ko with makes the car vibrate too much, ask ko lang kung may nakakaalam kung saan ko makikita ang idle adjust screw sa carb ko and anong direction ko dapat iikot para tumaas ng kaunti idling ko.

Pag nakatayo ako sa passenger side ng engine, may nakikita akong color gold na screw sa ilalaim ng air filter cover sa side ng valve cover na aboout 45 degrees un angle, un po ba ang idle adjust screw? Thanks po uli mga tsikoteers!

Dear joyluck614:

1st make sure to change your oil regularly as well as your air and oil filters - changing the fuel filter every 6 months or so wouldn't hurt either.

Have a tune-up done every oil change - clean and gap the spark plugs and make sure the timing is correct.

If your engine still has contact points, make sure they are NOT pitted and that the dwell angle is correct, and check if the condenser is still ok.

As much as possible, do NOT play around with the exhaust system if you want good power response and fuel economy - oversized mufflers look and sound great but perform poorly.

There are 2 screws that help to control your curb idle (that is the idling when the car stands still and the engine is running).

1st is the IDLE SPEED screw, you can find it by taking off the air cleaner assembly and then following the accelerator linkage to the side of your carb.

It is attached to the linkage system and moves the throttle plates (butterfly's) open or closed.

You will need a long flat screwdriver to adjust it (I know of no standard carb that uses philips head screws for adjustment).

Turning the screw clockwise speeds the curb idle up, counterclockwise slows it down.

The other screw (the bright yellow one you mentioned) is the CURB IDLE MIXTURE screw, it is yellow because that is the color of brass, which is generally used in valve materials.

If the idle system is working properly, generally you should not have to adjust this screw very often.

To adjust your mixture, use this procedure.

When you have done all the above, turn the IDLE SPEED SCREW clockwise to speed up your engine - because you said that it runs too slow.

When the idle speed is correct (check your tachometer), then you can set the IDLE MIXTURE screw.

Turn the screw (clockwise to close) in step of 1/4 turns until the engine starts to shake, - that's lean misfire, indicating that the mixture is too lean to fire evenly.

Procedure - turn 1/4th in, check for shake - if no shake, turn another 1/4th in, check for shake - if no shake, turn another 1/4th in and so on.

When engine starts to shake, back-off (turn the screw counter-clockwise) 1/2 turn and you set the curb idle mixture correctly.

Regards,

Dusky Lim

[joyluck614]

Dusky Lim,
Thank you for helping me out and all the tips you also gave me, worked out great, thank you and god bless

[duskylim]

Dusky Lim,
Thank you for helping me out and all the tips you also gave me, worked out great, thank you and god bless

Dear joyluck614:

You are very welcome.

Madali magbigay ng advice sa iyo because your car is easy to repair and the problem was relatively simple.

Best Regards,

Dusky Lim

[theshepherd]

Sir, what is the ideal idle speed for 12R engine? Mine reads 1000-1100. I want to bring it a lil bit down to decrease fuel consumption. Would 800-900 be normal?
Thanks in advance.

[duskylim]

Dear Sir:

900 to 1000 rpm is around normal for a 12R at FAST IDLE - when the A/C is ON.

When the A/C is OFF the idle speed should be around 700 to 800 rpm. That will help a lot with fuel economy AND make it easier for you to shift in traffic.

Your carburetor should have an FAST IDLE system - this is usually a solenoid-switched, vacuum-actuated diaphragm that pulls the throttle to a higher setting (higher rpm) for powering accessory loads like the air conditioner.

Note: this system is different from the one you previously adjusted the CURB IDLE with. It has it's own adjustment screw.

To look for the system, first set your curb idle to 700 to 800 rpm - like you did before. The CURB IDLE screw is always very close to the carburetor body and farther away from the throttle linkage.

Then with the air cleaner assembly removed, and the carburetor throttle linkage exposed to your view, have someone inside the car turn on the air conditioner.

You should notice the 'click' of the solenoid and some movement around the carburetor's throttle linkage system.

Look for a vacuum diaphragm that pulls the throttle shaft to a higher setting - you can't miss it if you know what you are looking for.

That's the FAST IDLE SYSTEM.

There should be a screw ON THE LINKAGE that allows you to adjust how fast the engine runs when the system activates - it is somewhere there among the throttle stuff. This screw is farther away from the carb body.

When you think you have found it, try adjusting it and see if the idle speed changes ONLY when the A/C is ON.

When you have found it, adjust it to 900 to 1000 rpm.

That way the engine will only speed up when the A/C is ON.

Hope this helps.

Dusky Lim