The 4 cylinder has a timing belt
timing CHAIN
The 3.8 liter V6 engine in a 1991 Mercury Cougar has a timing CHAIN
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
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 )
It has a cam chain that normally requires no maintenance.
Chain and it is a very (~1000.00) costly fix.
Dual chains
Timing Chains (2) with respective guides, tensioners and sprockets.
The V6 uses chains. The I4 uses belts.
The 2.0 litre four cylinder engine in a 2000 Mercury Cougar has a timing BELT
The 2.5 liter " Duratec " V6 engine used in a 1999 Mercury Cougar uses ( 2 ) timing CHAINS , both located at the front of the engine ( 1 chain to each cylinder head )