I have a 97 2.4l Tacoma with 240k miles. After an oil change and filling up the radiator (pretty low) the engine started to misfire later that day. Haven't had any signs of rough idle or misfires prior to this. Misfire code p0304 cylinder 4 misfire was detected. Changed plugs and fuel injectors and still misfires with same code. Ran a compression test prior to those changes and got 120ish reading in 1-3 and about 80 in 4. After I changed the plugs and injectors I ran a compression test again with all the plugs out and got 140ish in 1-3 and 0 in cylinder 4. Does the bad compression in 4 and the low coolant mean a blown head gasket? What else could it be or is there a way for me to determine head gasket before I start tearing it apart? Thanks for the help.

 

Pretty sure you have a bad HG, but do an exhaust gas test on your coolant (sold in auto parts stores) and that will nail it down.