1998 Dodge Other Overheating

I have 98 dodge grand caravan. It started to overheat when driving. Period. We replaced the thermostat. Did oil change and replaced coolant in radiator. Then replaced the cooling fan relay. The check engine light was still on, but no codes show when the auto parts guy hooked up the tester, and the ac still wasn't blowing cold air. If you check the fans with 12v they work. So we ordered an ECM online and followed the directions to change the computer. The van stopped overheating and the ac blows cold. However it started having a whole different set of issues. Throttle wasn't responding. Jerky. Sounded like it was misfiring. And then got to the point where it was shutting down at an idle, and did not want to drive period. In 2 days time of changing the computer. My husband put the old ECM back on and the new problems ceased and we are back to the overheating. The fans did not run with either computer unless we wired them directly to a 12v.

We are a single vehicle family with 2 toddlers and the heat indexes have been 100° + and I am terrified of taking them anywhere. Any help would be greatly appreciated!