My car has a rough idle. I believe it's because of my injectors. It's a 1990 300zx Twin Turbo. If it's just one injector that's bad can I replace just one injector without replacing all? Also my car is having a hard time starting. when I turn the key it wants to start but it won't so I give it a couple steps on the gas pedal and then it will eventually turn on. But when it's on the idle is rough and when you step on the gas a little bit the RPM's drop a little. My car had a engine swap done by a shop last year and the person who I bought the car from never drove it unless he had to move it. So it had 1 year old gas in it and the oil is dark. I replaced the gas with new gas and put fuel injector cleaner in it. And I am soon going to replace the oil.