Cylinder 4 Misfire code 304

My Tacoma has over 200k miles and it started to skip. So I changed plugs and wires as expected. Now I'm no slouch when it comes to being a mechanic. I also own a '69 F-100 that I have rebuilt the motor and made it a hotrod toy, but I digress. After changing the plugs and wires in my Tacoma, the truck ran fine and the check engine light went away for two days. Then the skip came back with the same code and a 1304 code. (If I remember correctly) This showed me cylinder 4 misfire and misfire on the corresponding coil pack. So I ordered and replaced all three coil packs. Still getting the same codes. FYI, the engine doesn't run hot and there isn't any water in the oil or vice versa. Also the truck will crank and run fine while cold, but once it is at operating temp., it starts to skip. Thinking that it could be a possible bad plug or bad coil pack, I replaced each with a new one and still have the same issue. I have had people tell me that it is the crankshaft sensor, fuel injector, ECM and MAF sensor. Any advice on the next possible step that will fix this issue is appreciated.

 

have you tried listening to the #4 injector with a piece of tubing or stethescope to see if it stops clicking at the skip ?

 

also check to see if the motor you have uses a VRS sensor or Hall effect sensor to trigger ignition
a VRS sensor can do this when they go bad ( it will act like skipping a beat at random instead of a pop like when a plug wire is jumping)
a Hall effect sensor will just quit, usually when hot

 

have similar issue but code indicates: "head gasket, #1 backfire", this after O2 sensor replaced, truck runs fine, hot or cold. have had obd read at Autozone and light goes out for a day or so then comes back on again, re-read and same happens, now is on for the third time. 2000 Tacoma 2.7L 84,000 miles. wondering what the dealer service dept will say.

 

a Hall effect sensor sends out a digital pulse , when the transistor fails it just shut off , engine dies . sometimes it will come back when it cools off . They are more precise than the VRS but the downside is that they need to be in a friendly environment, cool and clean, high fail rate if subject to heat or magnetic grit or oil gets in
on the other hand a VRS ( Variable reluctance Sensor) sends out a varying voltage wave form that changes with RPM and needs to be interpreted by the ECU. They have the advantage of being able to handle harsh environment, heat, oil, grit. They do have a low fail rate but downside is that it is a coil sending out a wave form. Many things can alter the wave form and the result of a fail is difficult to diagnose. It cannot be tested without an oscilloscope and even then you would have to know what the computer is looking for. Often exihibits as a random miss