car cranks but doesnt turn over?

I had the same problem about 6 months ago. For me it was the timing chain that broke. I would check that. My dad and I (I did most of the work) replace it in about 2 day even with me working full time at my job but found out that 2 of the valves go hit in the process and took 3 more day to fix. The 3.1L engines are not spose to be interference 99% of the time so yours may be ok.

Try replacing the throttle positioning censor. I had that same problem and I did that now she runs fine. Good luck