P0301 cylinder 1 misfire on Gen 2 after new Denso coil and new spark plug

what plugs and where did you buy them?

 

Lack of adequate engine lubrication can sometimes trigger a misfire code... Or a bad ignition coil can cause the problem, which you diagnose by moving the coil from misfiring cylinder to a different cylinder and see if misfire error moves to where you moved it or stays in place.

 

Just because it says Denso on the box doesn't mean it is a genuine Denso product. eCommerce sites are full of fake name-branded look-a-likes.

Amazon does not put a whole lot of effort into ensuring counterfeit products are not being sold through their channels, sad to say. Maybe one day that will change. eBay is even worse.

I'd suggest you pay a reasonable price at a bricks-and-mortar store and ensure you buy the real McCoy (genuine product).

It is not hard to tell if a spark plug is genuine just by looking at it if you know what to look for. The counterfeiters put more effort into making the box look real than the actual plug. LOL.

 

This is your likely answer... Though one time I did a full engine cleaning and tune up and new spark plugs on my Subaru that had a warped head and all the tinkering was enough to push the engine over the edge and could no longer find replacement heads so became a Prius driver instead.

In terms of next steps, reinstall your old coil and plug in that cylinder to confirm it's counterfeit/defective parts and if problem is still the same it's time to do a bore scope and compression test to confirm engine is ok.

 

that was my concern as well

 

dealer only, the supply chain is messed up

 

Numbers that are near the same across all four cylinders is what matters most...

 

With Amazon, it doesn't seem to be necessarily useful even to go by seller reviews and pick a specific seller ... because if they have seller A and seller B who list the "same" item, and you order it "from" seller A, and Amazon sees that they have seller B's stock in a nearer warehouse, it's possible they might just send you that.

The Automotive Anti-Counterfeiting Council whitepaper linked above kind of tiptoed around the actual name(s) of the "at least one" online marketplace that does that, but I'm pretty sure I've had it happen to me, when I ordered on you-know-where.

 

That's relatively common with all Prius / atkinson-based engines.

 

I had an engine rattle/shake at idle that was intermittent and came with CEL misfire codes for 1 and 3, I was worried it was a head gasket just from all of the Gen 3 videos. The rattle is not to be confused with the engine starting and lurching the car forward sometimes in park. I tried new plugs, coils, and fuel system cleaner with no luck, but a $40ish set of 4 refurbished fuel injectors solved my problem.

Mine sounded like this: