Engine 2.3l 1988 mustang lx cold start problems and bad idle.

There can be a lot of reasons for hard starting, and extreme cold or heat can exacerbate those symptoms.

The most common problems are vacuum leaks, and they are generally easiest to test for. You can google different methods if you are unfamiliar with looking for them.

I would also make sure that You don’t have worn ignition components. Worn spark plugs and wires can cause starting problems.

One thing that I personally encountered while battling an issue like yours was clogged fuel injectors. The car was very hard to get started and keep running, but once it got going it smoothed out. This problem continued to worsen, but was fixed after I replaced the fuel injectors.

You should also try to pull any check engine light codes to help with diagnosis.