Timing has to do with running, not cranking.
If this is a slow crank, it is either a mechanical problem such as binding, too heavy of an oil for the conditions, or lack of electrical power for the starter to spin adequetly.
I would change the oil first.
This is the spec for your car:
Below 14 F (-10 C), 1990-91 5W-20, 5W-30
Thursday, January 7th, 2010 AT 8:27 AM