The Pontiac Sunbird is built on General Motors J-body platform which it shares with sibling brands under various names.
The Sunbird depending on the model year came with one of these engines: 1.8L I-4, 1.8L I-4 (Fuel injected), 2.0L I-4 Turbo, 2.3L I-4 DOHC "Quad4", and 2.4L I-4 DOHC "Dual Cam" or "Twin Cam"
After 1994, the Sunbird name on Pontiac's J-body car was replaced with Sunfire. It could be suspected that this was done to avoid possible confusion with the Firebird, which was another model Pontiac produced.
See also
Pontiac 2000
Pontiac Sunfire