Removing the motor on your own is a daunting task, and it is not an easy way to answer this as it didn't specify what year and trim level Prelude in the question. My suggestion if you decide to do this is to pick up a Honda Prelude service manual for whichever particular year Prelude you own. This comprehensive manual is often used by authorized Honda service departments and auto enthusiasts that want to do their own repairs. replacements, and maintenance.
The 1986 Honda prelude 2.0 Si has a A20a3.
You need to specify what year Prelude as it varies how to remove a heater from generation to generation.
A 1994 Honda Prelude S would not have a VTEC engine in it (assuming it has the original engine in it). It should have the F22A1 in it which is SOHC and Non-VTEC.
possibly
Yes, All H and F series engines are interchangeable.
On the Prelude there are 2 O2 Sensors. They are on the exhaust manifold on the front of the engine. You will need to remove part of the plastic air intake in order to reach them.
None of the dashboard lights work on my 1988 Prelude. Why?
You could, but because the '94 Prelude is heavier than the '89 Prelude, it doesn't make sense to swap in a smaller powered motor.
very carefully
Yes. The H22a and H23a motors can interchange transmissions.
Have the car taken to Authorised Repairer for the Honda Cars. They can find out what has happened to the engine.
How can I check the ENGINE COOLANT TEMPERATURE (ECT) sensor on my 1991 HONDA PRELUDE SI 2.1L