Adjust of idle mixture

General discussion about our beloved Tercel 4WD cars
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Jojje_swe
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My tercel:: Tercel 4wd 1985

Adjust of idle mixture

Post by Jojje_swe »

What is this screw for? Found it when i looking for the adjust idle mixture screw. Can i use that one or is it the screw below that look like half moon? Does it look like this when the plug still is there?

https://ibb.co/b1D6Yz
https://ibb.co/b6E26K
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Petros
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My tercel:: '84 Tercel4wd w/extensive mods
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Re: Adjust of idle mixture

Post by Petros »

I do not think that is the mixture screw, it may be, but I do not recognize it. what country is your tercel from? there are several emissions/fuel system packages depending on what market they were built for. it might be why I do not recognize it.

In North American the idle mixture screw is in the throttle body assembly in the base of the carb, it gets a soft plug over it so it can not be adjusted from the factory setting. During a carb overhaul you have to drill out the plug to be able to remove the mixture screw so you can clean out the idle port.

You should not really need to adjust idle mixture, you just need to be able to set the normal idle speed, and the fast idle. the air/fuel ratio is determined by fixed jets throughout the speed range.
'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)
Jojje_swe
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My tercel:: Tercel 4wd 1985

Re: Adjust of idle mixture

Post by Jojje_swe »

I live in Sweden and the car are sold new here, it s 1985 model year. I have look in the factory service manual pdf here at the forum and that show the screw below the one i poiting at in picture. But nothing in pdf that I can found decribe the one that I point at it and not even look like it. My have o spring. As you mentioned I alsow thougt it may be somthing for swedish market. Dose anybody else know or seen it?
If it is the screw below as the pdf factory manual describe, should it look like my in the pic as a half moon or is it the plug? Difficult to drill then, thougt it should be flat plug head.
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dlb
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My tercel:: '87 sr5, '83 dlx parts car
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Re: Adjust of idle mixture

Post by dlb »

Hi Jojje. I agree with Petros, I have never seen a screw like that, or the half moon thing, on our North American Tercels so I think it is unique to Europe, or possibly Sweden itself.

There have been a few other members on this forum from other Scandinavian countries, like Norway and Iceland in particular, so your best bet might be to do a search on this forum for those countries, find those members, and send them emails or private messages to see if they have something similar on their Tercels. They are not on the forum very often so they are unlikely to see this thread but may still be of help if you can get in touch with them.

Good luck.
Jojje_swe
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Joined: Mon Jan 29, 2018 11:35 pm
My tercel:: Tercel 4wd 1985

Re: Adjust of idle mixture

Post by Jojje_swe »

Thanks for the answers, I have send a question to a swedish member here at the forum if he know somthing about the screw. I alsow went to toyota in my town but the car was to old for the mechanic and they could not find any book for my car that decribed the carburetor adjustment.
The reson I want to adjust is beacuse during the inspection i only hade 0,2co on the exhaust value. I was thinking to raise it to at least 1.5co. What do you have for the value of your cars?
Folian
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My tercel:: -87 swe t4wd

Re: Adjust of idle mixture

Post by Folian »

Hi Jojje,
Sorry I don't know enough about the carb in our cars. I just keep mine running until I can complete an engine swap to get something fuel injected.

maybe you've already tested all of the things below, but just to check...
My "relative wisdom" is that fueling/idle problems are rarely rectified by fiddling with adjustments on the carb. so I would start by just checking for a possible other cause of it not idling right:
bad spark? (circuit breakers (what's the English word for brytarspets?), coil, sparkplugs?

bad fuel supply?
clogged filter. clogged vent (I've had idling problems when my tank was building too much pressure after the tank vent was clogged. just try running it without a fuel filler lid.)
Making sure linkages are actually able to move freely.

and lastly, that intricate maze of vacuum line that goes everwhere… I don't know what does what but the service manual is your friend here.
Just make sure there are no vacuum leaks and that everything goes where it's supposed to. (I have a ke30 that I bought with a healthy 3A engine swapped into it. and it runs like crap, which I have always assumed is due to the lack of correctly plugged vacuum lines.)


Sorry I could be of more assistance. Lycka till!
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dlb
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Re: Adjust of idle mixture

Post by dlb »

Folian wrote: Mon Aug 13, 2018 1:01 am
and lastly, that intricate maze of vacuum line that goes everwhere… I don't know what does what but the service manual is your friend here.
Just make sure there are no vacuum leaks and that everything goes where it's supposed to. (I have a ke30 that I bought with a healthy 3A engine swapped into it. and it runs like crap, which I have always assumed is due to the lack of correctly plugged vacuum lines.)
I like this advice. The vacuum lines are very easy to mix up, and it can have all kinds of strange consequences. Use the service manual to make sure that all of yours are hooked up correctly. While you're at it, make sure that the various diaphragms still hold vacuum fine. To do this, I use the gross farmer method: suck on a hose going to a diaphragm and plug the end with your tongue. If it holds pressure, it's good. If it doesn't, it's bad -- in that case, just plug the hose that goes to that broken diaphragm for now.
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