Hi y'all! Got a question, kinda long, but alas, here we go.

I bought a 95 Concorde, 3.5 from a one owner 3? years ago. Always had this odd shift from low to 2nd. Would kinda shutter but never more but for just an instant.

Only till recently, for some reason, the "check engine" light will come on when it shifts now, sometime right at the time of shift, sometimes it'll go for some time before coming on. Oddly, it seems to not come on right away if 1) it's not been driven for a couple days or 2) it's really cold and it'll go several miles before lighting up.

It had just over 100,000 miles on it when I bought it, has 145 now. Fluid and filter were changed probably 30,000 miles ago.

Why now would the check engine light come on when it shifts? I can leave it set and run in the driveway and the light not come on, only after you've moved and shifted.

Thoughts?