OBD code PO455

P0455 - Evaporative Emission Control System Leak Detected (gross leak)

This leak refers to the vapor recovery system, and the leak is more than a loose hose clamp or pinhole leak in a hose or valve. Many large leaks can be found with a visual inspection. These leaks allow fuel to evaporate into the atmosphere. It has nothing to do with causing misfires.

Basically the EVAP test is simple. In your vehicle you have a leak detection pump, a tank pressure sensor and a purge control solenoid and a vent solenoid. To run the test the ECM closes the vent and purge solenoids and the pump starts running. The ECM times how long it takes for the tank to reach a desired vacuum level. It compares that time to a table. If the numbers match up, No code.
If the numbers do no match you get a code based on what did not happen.
In your case you have a big hole somewhere that prevents the vacuum from ever being created in the tank. Smoke test would show it real fast.

Doc is correct stating it would not be the cause of your misfire codes.
Those will either be something like bad plugs, wires or distributor cap, low fuel pressure, dirty injectors or possibly carbon on the valves. Do not ignore the misfire codes, the excess fuel can damage the converter.
When was the last time that engine had a tune up?

There has to be a fault code, and it is related to emissions, if the Check Engine light is on. Be sure you are looking in the Engine Computer, not one of the other computers. Do you know how to read the codes directly, without a scanner?

Cycle the ignition switch from "off" to "run" three times within five seconds, without cranking the engine, leave it in "run", then watch the code numbers appear in the odometer display.

Here my take on the code and the symptoms if the canister purge solenoid is stuck open. It will allow vacuum to go to the gas tank all the time. That can set that code and cause a misfire from vacuum leaking into the gas tank when it should not. Also, the vacuum supply line from the engine to the canister purge solenoid is broken or not connected can cause the same issues.

1996 and newer models use three-digit fault codes that display in the odometer. You are the third person this week with a '97 model that appears to be still using the Check Engine light. I don't have an answer for that.

Count the flashes of the Check Engine light. They are two-digit codes. There will be a group of flashes, a short pause, then another group of flashes for the second digit. After a longer pause, the next code will flash the same way. The last code will be code # 55 which just means it's done. If you think you miscounted, turn the ignition switch off and back on once, and it will start over.

With Chrysler nothing is standardized.
For instance the three turns of the key will bring up the codes on a 2003 Jeep Liberty Limited but not on the Sport or Renegade versions in the US.

All depends on who's ECM/PCM they used and which option package it has.