Toyota Tercel consuming more fuel?

It can be vacuum leak issue.

Do you have a scan tool to monitor the fuel trim numbers? Are the plugs black and coated? How have yo determined it is burning twice the gas?

Without being able to monitor the data list from the computer it is hard to say what is going on. The two things that can cause this or the most common are the MAP sensor mounted to the firewall. It is a vacuum sensor that detects engine load. If the line leaks or the sensor is bad it will cause it to run rich. If the EFI water temp sensor is bad or biased to the cold side and not sending a .4 or .5 volt signal to the computer when the engine is hot it will make it run rally rich also.

This details will help.

Thanks.

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