To service the fuel injectors, it is important to let the fuel pressure out first because, with the engine off, the pressure may still build up. Disconnect the negative battery cable and take off the intake manifold plenum, making sure to cover the intake manifold as you lift it to keep foreign things out. Unplug the two quick connect fuel supply tubes that are at the rear of the intake manifold. If the injector connectors do not bear their cylinder numbers, mark them so you know which cylinder they manage. Loosen all the electrical connector outlets from the fuel injectors, plus the bolts holding down the fuel rail and remove the fuel rail from the top of the cylinder head by lifting. Remove the fuel injector clips using a tool and remove the injectors next. Use this method for any other injectors that still need attention. After that, inspect the O-rings on the injectors; if you notice any damage, you will need to change the O-rings and, in addition, any damaged injector clips need to be changed.