Debating if I just need a new car

I have a 1995 Mitsubishi Galant and when it is 50 degrees or colder I have to let it warm up for at least 8 minutes. If I don’t it will not go faster than 10 mph, what could be causing this? My stepdad said he put in a rebuilt transmission a year and a half ago.

Does the engine rev too fast when you’re trying to go?

If not, I’d start with the engine. I’d start with the temp sensor. That tells the computer the car is cold and allows it to ignore the upstream oxygen sensor and run rich until it warms up. And it tells it how rich to run.

thanks for your response I’ll start there.