Question on Carburetor tuning

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Dumindu
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My tercel:: 1987 Toyota tercle 4wd DX Wagon 1452CC
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Question on Carburetor tuning

Post by Dumindu » Wed Jun 05, 2019 9:43 pm

My car is a Toyota Tercel 1987 4WD 1452CC DX Wagon (AL25). It has a Aisan 14120 two barrel carburetor.

Is there any rule to tune the carburetor?

I have heard that

1. Get the Idle Mixture Adjustment Screw to the fully closed position

2. Turn it 2-3 rounds to open

3. Then turn the Idle Speed Adjustment Screw to gain the best RPM.

Is the correct?

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NWMO
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Re: Question on Carburetor tuning

Post by NWMO » Wed Jun 05, 2019 10:00 pm

It may be, but my car came with a carb that includes solid plugs over the idle mixture screw and the FSM indicates to leave it alone unless there is a known problem.

That said, the idle adjust should be set to 800-900 rpm per the spec, but that’s pretty low. If you can set it around 1,200 rpm that seems to work well. Then set high idle per the FSM and you are ready to test drive.

If your car includes the TVSV you have to disconnect/plug a port as well.

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Petros
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My tercel:: '84 Tercel4wd w/extensive mods
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Re: Question on Carburetor tuning

Post by Petros » Thu Jun 06, 2019 12:31 am

the way you adjust the idle mixture is, with it at idle speed, you screw it in until the motor speed slows and get jerky, than screw it out slowly, counting each turn as you go. the idle speed should smooth out, and than get rough again as you screw it out further. than you screw it back in exactly half way between the lean rough spot and the rich rough spot.

than you reset the idle speed so it is correct.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)

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Dumindu
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My tercel:: 1987 Toyota tercle 4wd DX Wagon 1452CC
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Re: Question on Carburetor tuning

Post by Dumindu » Thu Jun 06, 2019 1:16 am

Thank you all for valuable advises.

Is there any rule for Idle Speed Adjustment Screw turning (After Idle mixture screw is adjusted)?

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Petros
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Re: Question on Carburetor tuning

Post by Petros » Thu Jun 06, 2019 5:15 pm

idle speed is set per the factory spec. I have noticed however on older worn fuel system you may not get a stable idle at the factory spec, so I always set it a bit higher, like at 800-900 rpms.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)

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Dumindu
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Posts: 167
Joined: Wed Aug 02, 2017 12:34 pm
My tercel:: 1987 Toyota tercle 4wd DX Wagon 1452CC
Location: Sri Lanka
Contact:

Re: Question on Carburetor tuning

Post by Dumindu » Thu Jun 06, 2019 6:20 pm

Again, thank you very much.

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