Gen 3 prius misfire at highway speeds

It would be almost a miracle at this point that the problem is not a failed head gasket.

I would definitely try and clean out the EGR system and Intake manifold, change pcv valve while you're in there. you're about 100k miles overdue for that cleanout. It should be completely blocked up with carbon

 

Try a leak-down test. With EGR cleaning neglected this long, it's near certainty it's the head gasket. See first link in my signature for EGR cleaning, but the head gasket should be first priority.

 

The cold start severe rattling is the clear sign of a normal Prius head gasket failure. They rarely repeat every day, sometimes going weeks between events. But when they do have a cold start rattle it is severe. Coolant does not go down enough to notice under these conditions, confusing everyone that has not seen it before. It seems to seal itself after very little operation.

However if it is only misfire coding at highway speeds it is possible something else is at fault. Counterfeit plugs. Possible egr sticking open. Not an egr clogged. Egr flow is closed at low speeds and wide open throttle. So if it is open at those times the engine will run badly. The Car Care Nut egr video describes a simple egr blocking method to isolate a sticking open issue.

 

With 230K miles, the EGR cooler will be a "blocking method", without any help, lol.

 

Start looking for a Japan domestic market 2 zfxe. You will be needing it as doing the repair digging a little deeper looking very good at your number two piston and it's bore and you may find it's not worth it to have someone in the United States to do all this repair work because that can go south very quickly and you still wind up needing an engine so if you don't have money to play with and money to burn. I'm telling you one of the cheapest outcomes you're going to have won't you start paying people to shave ahead do a head job then it turns out you got problems with the number two slug or piston. You're going to be all in around 3,000 or better you can have an engine and motor generator one and two transmissions sitting in your driveway for under $1,400 I just did this like 165 days ago the engines like brand new so is the transmission I had almost the exact miles you have on a 2013 and I have a 2010 with 260 k that's never had any work done driven by the old lady for doordash and all that nonsense it's a toss up there's no way to know until it's really time to spend the money that's how it works out or it will progressively get worse and you'll notice that switching between electric and regular driving and vice versa and all this a big clunk and a bunch of bumps and lots of noise and that does not seem to be too good on the drivetrain but go ahead and beat the heck out of it because you're going to replacing both pieces that's the cheapest thing to do really

 

Can you help me understand why half the people say a clogged EGR causes headgasket failure while the other half of the people say it doesn't? Or maybe a link that summarises both views? Or maybe start a new thread?

 

That's a tall order. I could tell you why I think clogged EGR is causing the head gasket failures:

1. 3rd gen head gaskets, the first gen with this new EGR system, are failing with tedious regularity.
2. The failures are happening unusually early.
3. No hard stats to back it up, but from all reports I've seen here the EGR system had not been cleaned, or was cleaned way too late, or was only partially cleaned, and usually after head gasket failure symptoms had started.
4. Properly flowing EGR is said to be crucial for regulating combustion chamber temps; the engineers are running the engines lean, and counting on the EGR when doing this.

 

Bad rings, bad cylinder design for a stop start engine, intake manifold liquids and serious thermal cycling. Egrs are a side effect although the fact they clog is a result of bad design. Toyota still does not recommend periodic egr cleaning. They do recommend new pistons and rings even when "just" the head gasket has failed. In many "head gasket failures" the metal head gasket is not blown but the aluminum surfaces it is trying to seal are warped. Which is why Toyota dealers and serious shops rebuild or replace.

 

Welp, just clean that EGR puppy every 50K miles, change the oil at 6 months or 5K miles, and let the chips fall where they may.

Works for that very elderly Priuschatter; his 2010 has 270K now.

 

Number 4 seems like the most clear explanation I've read so far... Now if we could find someone to help compare combustion temps in a clean vs. clogged EGR?

 

I tend to lean towards practical over theoretical: I want my car to last, and if there's a few "broad stroke" chores that stand a decent chance of accomplishing that, I'm all in. I don't really care about the minutia, just see a lot of corellation between clogged EGR and blown head gaskets. And, you see a picture of a cooler, that's supposed to be flowing air, and it's a carbon blob? That can't be good.

 

I'm curious if hybrid pit will rebuild your motor if you bring it to them? It might be worthwhile to let the professionals rebuild it, you just have to take it out and put it back in.

 

I've been hoping @Mendel Leisk updates all his links in his signature at the bottom of his posts... Hope he finds a good video for a leak down test too!

 

This is just one I’ve watched recently:

 

Yeah, that's the problem: it seems so clear ... but it is far far far less clear than it seems.

"Combustion chamber temps" can mean two very different things: the temperature of the combustion chamber, or the peak-for-mere-microseconds temperature of the gases in the combustion chamber during the few crank degrees out of every cycle where the temperatures are anything like that.

We know that EGR brings down those instantaneous peaks, by enough to stop NOx emissions from forming (because that's one of its prime reasons for being there).

The head gasket, though, is going to stay much more at the temperature of the combustion chamber, sandwiched as it is between two large chunks of aluminum with thermostatically-controlled cooling water pumped through them. And that temperature is much, much lower than the instantaneous peaks of the burning mixture, and it is much, much less affected by EGR than the instantaneous peaks.

Of the whole head gasket, only the inner edges of the metal rings that make the edges of the cylinder bore holes are ever even exposed to the gases in the combustion chamber that ever reach those instantaneous temperature peaks.

There is very little usable information to be found on PriusChat about whether combustion chamber temperature effects of EGR are even a plausible mechanism for head gasket damage or not. There are probably people in automotive engineering who could address that question knowledgeably, but none of them have stopped by here.

However, there is another phenomenon—detonation—that is known to be associated with insufficient EGR, and is also known to be a cause of mechanical damage including to head gaskets. That, I have been able to find literature references supporting. That's what the Prius ECM is trying to avoid, when it dials back the ignition timing if it sees a failed EGR flow test.

 

Yes all valid points... Though I've yet to see people explicitly say I constantly clean EGR and use oil catch can and still had a blown head gasket. Though it's clear that people who have had at least one EGR cleaning have had a blown head gasket. Not sure of the details/proof as cause and effect though.

So I guess the answer to the question is that it's a little bit of everything that led to a bad initial design for the Gen3 engine, which doesn't run optimally once the EGR is clogged. Or as was said in this thread: