epic trails

im a recent honda convert, i have been driving mkII volkswagen gli's til now. i just bought a '92 civic hatch that my buddy rebuilt with upgraded gsr suspension and a d16 z6 (hoping for something bigger soon). i needed reliability and decent milage - drove from maine to colorado for school. somewhere in nebraska i ran into traffic from an accident and my idle dropped to about 400 rpm. the car made it fine the rest of the way, but when its warm the idle stays around 400. when the motor is cold the idle is regular until it warms up. for thought was the coolant but that's where it should be. i appreciate any input and advice you guys might have and im sure ill be back for more.