From what I was told the 3.1 came with only the 3 speed automatic except the ones that came with manual shift and the 3.4 came with the 4 speed automatic and also a manual trans. I had my 3.4 removed and the 3.1 installed and I don't know how or what they changed with regards to the computer. I bought the first 3.1 from a yard in another state it came with ECM and some other parts as this one was broken (freeze plugs) and it was needed for the accessories , brackets, mounts etc. The second 3.1 was bought from another yard and it was pulled and shelved from a 1993 lumina that was hit in the rear some years prior with only 19,600.
Yesterday, I pulled the overflow tank so I could inspect the ECM, wires etc. I didn't see any intrusion to the wires so I raped on the ECM got in and started the engine and for a split second it ran rough but then it was perfect just like it was prior to Wednesday. I feed it throttle and it ran perfect. I copied the information off of my ECM so that when I order the AC Delco ECM they will have the info that's needed. I will then change the prom, as I watched a YOU TUBE clip where the guy changed the prom from a 1993 Buick's ECM. I will do the install and hope for the best. Also I cleared the codes and will start the engine today to see if they return. As of now there is no dash lights on. Thanks to all for your help
