I have a 1998 Pontaic Grand PRix and the Service Engine Soonlight comes on and I had it tested and it says the it has a misfire on Cylindar 4 and the Transmission Torque Convertor solenoid was stuck open I have put new spark plugs and wires on it How do I fix this

You will need to have the coils checked, a quick test would be to swap coils and see if the misfire moves to another cylinder and if that happens then that would tell you that the coil is bad, for example a coil runs two cylinder if you take the # 3 coil and swap it with another one and then scan the codes and see if the misfire changes to the cylinder you swap it to then coil is the problem for the misfiring. when changing coils if this has no change then make sure to have the fuel injectors cleaned, this is the other most common reason for misfires, dirty injectors are very common on these engines. the converter problem is something else, you will need to replace the converter solenoid and check the wiring inside trant going to solenoid, you will see the wiring harness, check it for broken wires, if you replace solenoid and wiring is good then you will have converter problems and may need a trany shop to look at it but most common reason for this code is the solenoid . good day

Was the col tested for that plug
torque converter selenoid stuck open you have to change it