The 89 2.3 IS an interference engine. I would replace it ASAP
There is also a TSB that might interest you.
February 26, 1992
^ TIMING BELT - 2.3L OHC - "WARBLE" SOUNDS FROM ENGINE COMPARTMENT
^ NOISE - "WARBLE" SOUNDS FROM ENGINE COMPARTMENT
FORD: 1985-88 THUNDERBIRD 1985-92 MUSTANG
LINCOLN-MERCURY: 1985 COUGAR
MERKUR: 1985-89 XR4TI
LIGHT TRUCK: 1985-92 RANGER 1986 AEROSTAR
ISSUE: A "Warbling" sound may come from the engine compartment. This is caused by the timing belt design.
ACTION: Install a new design half-round tooth timing belt (F1ZZ-6268-A). Also replace the crankshaft sprocket (F1ZZ-6306-A), camshaft sprocket and auxiliary shaft sprocket (F1ZZ-6256-A) to accommodate the new half-round timing belt. Refer to the appropriate Car or Light Truck Service Manual, 2.3L OHC Engine Section, for service details.
PART NUMBER PART NAME CLASS
F1ZZ-6268-A Timing Belt CG
F1ZZ-6306-A Crankshaft Sprocket CG
F1ZZ-6256-A Camshaft And Auxiliary CG
Sprocket (2 Req.)
OTHER APPLICABLE ARTICLES: NONE
WARRANTY STATUS: Eligible Under Bumper To Bumper Warranty Coverage
For 1992 Models, Basic
Warranty Coverage, Major