Poor gas mileage

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SirFoxx
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Posts: 81
Joined: Sun Feb 05, 2017 5:42 pm
My tercel:: 1981 Toyota Tercel w/ 7age

Poor gas mileage

Post by SirFoxx » Wed May 30, 2018 2:16 am

Hello--

I recently acquired a 1981 base Tercel w/ 3ac and 4spd manual. I've been having to drive it since my wagon got mushed by a drunk driver (story for another thread). I just started tracking the mileage, and I'm getting around 18mpg.

There have been no mods done to the car, except a 2.5" stainless exhaust by the po. I've had the replace the secondary diapragm (still don't think it's working right) and a diapragm on the front of the carb (can't remember the acronym for it--i knew it was bad since there was gas in the vacuum line, and it was disintegrated). Someone on the Facebook group sent me pictures of where the vacuum lines go, and from I can tell, all the lines are hooked up correctly. Lastly, I did check the vacuum advance w/ a timing light, and it does work.

The only odd things that it does is, when coasting in gear, foot off the gas, it gurgles and pops out the exhaust, though I didn't know if that was a side affect if the large, throaty exhaust. Also, it does have a slightly high idle, though I think that's because the return spring can't fully close the butterfly valve as I can go under the hood and push down on it, and the throttle will come down.

Aside from putting a Weber on it, what could be causing the poor gas mileage, and is there anything else I can check on the carb / vacuum system?
1988 DLX Tercel Wagon w/ weber (RIP)
1985 4wd Tercel SR5 (RIP)
1981 Toyota Tercel

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Petros
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Posts: 11103
Joined: Sun Jan 28, 2007 6:31 pm
My tercel:: '84 Tercel4wd w/extensive mods
Location: Arlington WA USA

Re: Poor gas mileage

Post by Petros » Thu May 31, 2018 10:25 pm

I have seen other forum members had bad economy when the device in the canister behind the rad overflow tank go bad, it has vac lines and electrical lines that go to it. it is called something like EBVT or some such acronym. it controls mixture by bleeding air under the carb to vary the airfuel ratio. it if goes bad it will cause the fuel economy to go bad, likely it fails in a run rich mode.

I do not know if it can be bypassed, may need to replace the device to get it run correctly. or go weber.
'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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