2010 Prius; Whole-vehicle shudder, P0304, seems unrelated

Yep, made sure every orifice of that thing got attention.

...and dammit, "that's what he said"

 

Sorry, couldn't resist a "that's what she (he) said joke".

And if it was an orifice on that intake, it got blasted. Most of the gunk came out of the smaller connection to the EGR on one end tho.

I honestly can't remember what orifices this thing had, it's been a few months ago. I remember giving full attention to every angle I could get into the thing, tho.

 

The misfire & "shake" (we confirmed by watching the misfires on Cyl4 count up by a dozen or more PER SECOND at a time on a test-run) were getting so bad I was concerned about even driving it.

So...latest from a (another, who I trust more) local mechanic, I couldn't make it into town this week to take it to Toyota.

Plugs were "all shot" (he replaced 'em)
Coils, he swapped around (and has his OWN curiosity as to whether that previous mechanic did either of those). Issue stays on Cyl4.
Compression & timing are right where they should be (his words).
An the injector "test out fine"...which doesn't really mean much since you can't actually see if it's spraying without removing it...just whether the electrical components are doing what they should (on this particular "type" of injector?)

And of course, since we're in the sticks, it takes a couple of days to get a replacement injector in. Which would be the next step.

Says it's not lack of airflow, as that spark plug would be "fat" (his term, meaning soaking in unfired gasoline)...which wasn't the case.

I'm betting on a replacement injector (arrives hopefully tomorrow) fixing this even tho above "tested out fine"...either partially or mostly clogged, since if you "push" it past the point where it's misfiring...it "steadies out" and the misfires stop until the RPMs drop into that range again.

Any ideas on other avenues to pursue?

If I end up having to get it to Toyota, I'll probably have it towed into town.

 

Is words were "swapping an injector is such a pain, we might as well just replace it.

I agreed with the sentiment.

 

The other 3 are giving a big fat zero on misfires, tho. And at a bit over $100/each, that's a bit much.

Wouldn't wiring problems result in a failed electrical test of the injector itself (which I guess is done thru the scantool)?

 

After getting a message from the Prius tech about those passages being blocked, I took a closer look at picture (close-up) of those tiny holes you mention...and I can't remember cleaning them. I can't remember even seeing them!

Is this the 1/4" passage(s) you're talking about? Actually "inside" the larger port-openings themselves?

BTW, Pics pulled off Google, these aren't my car.

https://images.app.goo.gl/UgmNennEiuSdNSj17
https://images.app.goo.gl/KFSS9PgSVqbTKn3MA
https://images.app.goo.gl/W7y2k6NmNZ7cPQXF8

 

Searching through old threads, I found this one that described my symptoms EXACTLY.
https://priuschat.com/threads/missing-under-light-throttle.153305

Here was my contribution to that thread a little bit ago...
missing under light throttle | Page 2 | PriusChat


And then I got this video from Toyota like 5 minutes ago that explains it all & puts it all together.

3 of the 4 ports are either fully or partially clogged (that little 1/4" hole in the Intake Manifold you mention, Mendel I'm so sorry I misunderstood when you mentioned it before)...and the 4th port gets all of the EGR gas...full of carbon monoxide, meaning there's next to no OXYGEN in that cylinder when it tries to fire, hence instant misfire.

EDIT: It won't let me include the video, dammit!

 

Thanks for the suggestion of using a pistol-bore brush.

Nope. "We don't clean parts, we just replace 'em" is essentially what they said. And wanted somewhere in the area of $2k to do it (and the EGR Valve too, even though that is DEFINITELY not the problem, more below).

Fortunately, they don't charge for diagnostic, even when it involves a tear-down. So worst-case I get it towed back out here to the hill-country mechanic who can take it apart again for a couple hundred(?)...I'll run it down to the car-wash & clean out those smaller passages...and we should be back in business.

In that other thread I linked above, another user explained what was puzzling me (and the mechanic), why the symptom only shows up when the car's "up to temp". The cause of the misfires is, 3 of the passages were either partially or fully clogged so ALL of the EGR exhaust gas was going into the one cylinder, causing that cylinder to get almost no oxygen...meaning instant misfire.

Well...Before the car warms up, it's in "open cycle mode(?)"...which means the EGR valve is closed, providing NO exhaust to the cylinder...which is why it wasn't misfiring when cold.

It's also how I know the EGR valve probably is fine...it's not stuck closed (that cylinder is obviously getting exhaust gas, otherwise I'd be getting no misfire), it's not stuck open (otherwise the misfire would happen all the time, even when cold)...so the EGR Valve is (theoretically) fine.

 

This stuff (or something similar)?

 

Well...after doing the intake cleaning (again, better), and boring out those tiny ports...I took it on about a 10mile testdrive, up to 60mph...not a single misfire...and I was watchin the individual cylinders.

And of course the "whole vehicle shudder" I thought was completely unrelated...is gone too.

Thanks all for the advice.