Hi,
It could be a few different things causing it. Based on your description, I suspect you feel this at a lower RPM. That could be the result of fuel pressure, a vacuum leak, engine ignition timing, and so on.
Therefore, let's first start by checking if there are any diagnostic trouble codes stored in the computer which will point us in the right direction. Otherwise, it becomes a guessing game and a lot of testing.
Follow the directions in the following link. You don't need a scanner to perform this process.
https://www.2carpros.com/articles/toyota-trouble-code-definitions-and-code-gathering-method-1990-1995
Let me know what you find or if you have other questions.
Take care,
Joe
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Saturday, July 17th, 2021 AT 10:18 PM