Honestly, anything is possible. You are certain that the throttle plate is closing, correct? Here is what the manual indicates for a high idle issue. However, red line usually isn't the case. The kick down linkage can cause a problem and you did have the trans out, so the easiest thing to do is make sure the throttle plate is closed.
1984 Toyota Celica L4-2366cc 22R
Engine Idle Speed Too High
Vehicle Powertrain Management Fuel Delivery and Air Induction Testing and Inspection Symptom Related Diagnostic Procedures Troubleshooting By Symptoms Engine Idle Speed Too High
ENGINE IDLE SPEED TOO HIGH
1. Accelerator linkage binding.
2. Air valve stuck open.
3. Improper operation of air conditioner idle up circuit.
4. Fuel pressure too high.
5. Cold start injector leaking.
6. Injectors leaking.
7. Defective EFI computer.
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Your vehicle is fuel injected, correct? This is near a time when things were changing. Did you by chance check to make sure the fuel pressure regulator vacuum hose is connected?
Fuel pressure at idle should be 33---38 psi. It may not be a bad idea to confirm it isn't high.
https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator
Let me know.
Joe
Thursday, January 23rd, 2020 AT 7:12 PM