Powerwashed engine and shortly thereafter engine was sluggish and CEL game on. Code P0304 came up. Google searched 97 Toyota 4Runner P0304 and it brought up several threads from this site. I've been reading and learning a lot just by using this site. I sighed up and this is my first post. I swapped the coil pack on cylinder 3 with the coil pack on cylinder 1. Reset CEL, drove for 10 minutes, CEL back on. Rechecked code and now I have a P0302. Does this mean definitely that it's a coil pack, or could it be something else? Model is Limited V6 with 185,000 miles. Thanks in advance.

 

That would be correct sir. Just for fun you may try taking the coil out and hitting it with a blow dryer. Not close enof to make it hot just dry it out. Then try it again. Heard it online, sceptical but still curious.

 

That code is for a misfire/fuel injector failure. Maybe you blasted water into the fuel injectors electrical connector. Try cleaning the connectors with electronics cleaner in a spray can and dab them with dielectric grease.

 

I had this code yesterday morning and today but only at start up when cold. I clear the code and does not come back throughout the day when starting. I have a 5vze with new plugs, boots and wires (all denso). I'll be swapping the coils tonight to see if the misfire moves to a different cylinder. Since it happens only during the first start up, I might have a dirty or bad injector. I don't believe mine is related to your problem but you might want to pull the top of the boots and use dialectric grease in them along with the plugs as well. See if that solves your problem.

 

Hey, I had the same problem. Started sputtering, then smooth, then sputtering again. Check engine light came on with P0304 code. Replaced plugs with no effect. Replaced number 4 coil, with no effect then replaced wires and that fixed it. Good luck guys, this seems like a common problem.

 

Number 4 coil? On the 5vz-fe, there is no such thing. Which one did you really replace?

The cylinders are numbered:
5 6
3 4
1 2
Front of engine

 

The #1 coil serves the #1 and the #4 cylinder. Excuse me for trying to help...