Need some advice

easiest way is to swap the coil to another cylinder. If the code reader has the misfire going to the new cylinder, then it's most likely the coil.

 

P0304 is a misfire specifically on cylinder 4. The most likely problems are a bad plug (already replaced), bad coil, bad fuel injector. Less likely problems are a leaking had gasket (check the ICE coolant level in the radiator and in the overflow tank) or a bad wire or connector going to that coil. If none of those are the problem check compression.

Be aware that Amazon and Ebay are awash in counterfeit Toyota parts. Much grief can be avoided by either buying from a Toyota dealer (often less expensive if ordered online) or from RockAuto (if going with an aftermarket part).

 

Aftermarket coils are cheap and work great because they are standard across many different Toyota models... As for counterfeit products, that's primarily an issue with spark plugs and not much else. But every aftermarket part is different and needs to be examined.

 

Counterfeits in fake Toyota packaging include air filters, cabin filters, water pumps and spark plugs.

Usually the fake packaging is not crisply printed and will typically say made in Japan when real parts are usually made elsewhere.

If you are paying 1/4 to 1/2 dealer from anyone but a dealer it is counterfeit.

 

I probably could be talked into taking the risk of a counterfeit cabin filter. Not much to worry about even if it sucks.

Let's not forget grass-clipping brake pads.

 

Well, normally anyway - worst case you are just breathing unfiltered air. However, the recent Eaton fire was not too far from us and there was a lot of crud in the air. The cars were running "recirculate" whenever we went out so that we didn't have to use N95's while driving. My son's CPAP machine has a filter, and even though it was inside 100% of the time with the windows closed, and the house was never directly in the smoke plume, it jammed up really quickly after the fire. When he pulled it out it was black. First time that ever happened.

OMG. First the car won't stop and then all the brakes go up in flames.

 

Maybe try this one? CF10285 Cabin Air Filter fit TOYOTA LEXUS CHARCOAL CARBON Fast shipping | eBay Only $8.99

 

Cheap aftermarket is a known risk.
Counterfeits are unknown unknowns.

 

I would think now that coil over the plugs should be a no-brainer in any idiot should be able to manufacture You can make up your own at the house practically I won't be as durable and what have you in packaged like the one specifically for your engine but still these things made by TRQ and all the other no name brand manufacturers these things aren't rocket science I mean if it's just a matter of picking crappy resistors and circuits just because you can well there you go maybe a manufacturer should stick to what they should that sort of thing I think that's what's kind of gone missing here everybody just plops out a bunch of garbage in hopes to sell a few pieces or something It's just almost nonsensical but it's where we're at.

 

Misfire can be caused by a number of reasons. Follow the instructions and you will win.
https://share.qclt.com/%E4%B8%B0%E7%94%B0%E6%99%AE%E7%91%9E%E6%96%AF%E5%8E%9F%E5%8E%82%E8%8B%B1%E6%96%87%E6%89%8B%E5%86%8Cpdf%E6%A0%BC%E5%BC%8F/repair%20manual/04pruisr/05/2054m/cip0300.pdf

 

My transistor fab is down for weeks any time somebody walks in with their shoes on.

 

Semiconductors are sensitive to insanely small levels of contamination. Thumb print on the wafer? Too much sodium, into the trash.

Coil packs are not that touchy. They are just two concentric coils of wire wound around an iron core, a spring, a bit of wire, an electrical connector, and some plastic to pack it in. Not very sensitive to contamination. Usually only one diode present. A crappy one will fail early because the manufacturer cut corners too aggressively on wire diameter, wire coating, or some other quality measure and it burns out, shorts out, breaks a wire (blocking a current path), or the connector parts corrode.

 

Did you replace the plugs with genuine oem from a dealer?

 

Say what? These are not just "coil packs" on our Prii; they are igniters, and include the circuit to power the coil primary from the battery and then interrupt it on signal from the ECM, and send the IGF confirmation signal back. Toyota's diagram leaves the rest of the driver/IGF circuit to the imagination, but definitely shows the important power transistor in there.

 

Simplified Coil Circuit

Waveform

 

Guess I got that one wrong. More electronic parts than a simple coil pack.

I don't understand that oscilloscope image.

IGF fires several times without corresponding IGT. Are all the IGF lines coming from the cylinders tied together into one input at the ECM?

Also the spark plug current spikes before the trailing edge of IGT and ends its spike right at that edge. Shouldn't it spike starting when the transistor between the coil and ground's control input goes from high to low? I can't read the numbers on the X axis. Is increasing time in that plot left to right or right to left? Where is +12V in the simplified diagram and does "ignition control circuit" invert the IGT voltage shown in the trace?

 

Yes you can see that in the Prius wiring diagrams.

The battery symbol is on the left.

Toyota Ignition Diagnostic article
Dotting the IGFs and Crossing the IGTs

 

My theory is that evaluating these aftermarket ignition coils is best done by weight. Because the more copper the coil has the better it will perform. What do you think?