PCM loses memory overnight but is fine during the day.

My 98 explorer has a problem of not being ready for the emissions test.
Every morning when I start it, it's acting as if it's re-learning the engine all over again, rough idle etc.
I checked the fuses in the power distribution box and their all good.
It's fine all day long, but if it sits more than 8 hours then it's back to square one again, the morning routine of letting the pcm learn the engine all over again.
I checked for any loose connections, and found nothing.

any ideas on troubleshooting the core problem? Is it the pcm?

I'm running out of time on the emissions test grace period. I'm a student and I cant afford for this truck to be down. Or any major repair costs.