I have a ’95 Honda Civic EX automatic, before I installed an aftermarket throttle body and intake manifold. Now I put back in the original throttle body and intake manifold and when the car was warmed up to a normal temperature and in park, the idle fluctuates between 500 to 1,000 rpm after hitting the gas a couple times. Also, while in park the rpm will sometimes fluctuate between 800 to 1,000 very slowly. If the car is just in park for a long time without hitting the gas this problem doesn’t occur. When I have the car in drive, the car idles fine; my only problem is when it’s in park.

 

make sure all vaccum hoses and wiring conector are connected.