I am getting a code P0306 on my 2005 Tacoma. I have replaced the plugs and moved the coil pack from cylinder 6 to cylinder 1 but the code still points to cylinder 6. The truck will stumble/miss at start up after it has been sitting for a while, but then once it has warmed up, it smooths out. I have checked the coolant for oil and the oil for coolant and there does not appear to be a head gasket issue as both the coolant and oil look normal. I am thinking fuel injector (I am at 172k miles). I am currently running fuel injector cleaner and tank of 93 octane through it hoping that this is just a dirty injector.
Now to my question: I have looked at the FSM and it indicates that the cooling system should be drained when changing out the fuel injectors. I have searched to see if there is any information on the site about changing out the injectors and the link below is the only thing I have found that is relevant. In looking at the link, I don't see anywhere that draining the coolant is required to change an injector. Am I missing something or is the FSM incorrect? While I am not an auto mechanic, I am fairly competent when it comes to mechanical repairs. I just don't want to drain the coolant if I don't have to and also make sure I have the tools/materials available to complete the job once I have started.