The 4 cylinder has a timing belt
It must have a timing chain because Gates ( they make timing belts etc. ) only lists a timing belt for the 4 cylinder engine on a 2000 Mercury Cougar
The 3.8 liter V6 engine in a 1991 Mercury Cougar has a timing CHAIN
Chain and it is a very (~1000.00) costly fix.
Dual chains
The 2.0 litre four cylinder engine in a 2000 Mercury Cougar has a timing BELT
It has a cam chain that normally requires no maintenance.
On a 1996 Mercury Cougar : The 3.8 liter V6 engine has ( 1 timing CHAIN ) The 4.6 liter V8 engine has ( 1 timing CHAIN to each cylinder head , so there are 2 timing CHAINS )
The 2.5 litre V6 engine in a 1999 Mercury Cougar has ( 1 timing CHAIN to each cylinder head , so there are 2 timing CHAINS )
The V6 uses chains. The I4 uses belts.
Timing chain.
Timing BELT