why does my 1990 honda accord smell like ammonia and has a poor idle
Mice.
Small animals like mice will nest in cars (engine compartments, etc) in winter and chew on electrical wires, rubber hoses, etc.
My parents had a Jetta that needed an emissions system (gas vapor return) hose replaced because mice had chewed through it. The symptom of that problem was that the inside of the car smelled like gas. The dealership had to remove the gas tank in order to replace the hose.
The Jetta lived in my parents’ garage, and I later found that the mice had been attracted to the garage by a bag of grass seed and another bag of birdseed, both of which they had been eating.
If you park your car in a garage, be sure to store any seeds in metal containers to discourage mice from taking up residence. The mice will gnaw right through plastic containers.