Hello eric, i have a 2000 kia sephia 4 cylinder 1.8 liter engine that has a very very slight idle and hesitation. I have changed spark plugs, spark wires, coils, injectors, mass air flow sensor, throttle position sensor. Did a smoke test and has no vaccuum leaks. It mostly happens when i amslowing down at a stop light. But i can also notice hesitation when i step on the gas. There is no check engine light. I have been stumped on this for over a year. Please help. Also i took it into the dealership for them to look over and they said it was spark plugs even though i just replaced those less than a year ago.i had them replace them and still the problem persists. Please help thanks