Ok guys i bleed the cooling system. cars running 190-195 but well under 210. I have been checking the coolant levels with no noticable drop in it. i have pulled the plug again its not cracked. new wires new fuel filter. i replace the #4 injector then take it to the local gm dealer where they also read p0304 they tell me it has to be the injector they inspect the plug wire and plug and coil also they say they are fine. that its the injector. so i replace yet again the injector not once but twice and i continue to receive p0304. I also get a random p0300 and have noticed the rpms usually staying around 900 rpms then it will spike to 1200 or so then drop down again. the spike in rpms is rare and have only noticed it twice. so I think im getting maybe bad injectors so i get one from different parts house thats 3rd new injector no change still throwing the same code. i have blown out the vaccum lines with compressed air. Exhaust is clear(no white smoke as from coolant. What am i missing? could it be fuel pressure reg? The car drives great tons of power only time you notice the misfire is at idle.
