We can only guess that the trailer disturbed the airflow from the back of the truck, which allowed some exhaust to invade the cab of your truck. The catalytic converter may have been overheated with the extra weight of the trailer thereby causing it to work at less than 100 percent efficiency now. Installed a trailer hitch and have a problem with wiring a 3 pole connector. 3 types tried so far with no luck. Latest is a plug-in type for an '88 Comanche.
Taillights are different.
I.e. turn signals and taillights work but no brake lights, or lights dim when engaging brake. Without looking at your trailer, we would guess that there is insufficient ground from the Jeep to the trailer lights. Run a ground wire from the frame of the Jeep to the housing for the lights on the trailer. What is the exact motor size of this van. The van I want is a Chevy Venture.