Finally the dreaded P0301 Code

Go borrow an inspection camera from AutoZone or any of those places if they do that they're pretty cheap now for a reasonably quality one unless you're going to live using it might buy a better one look in the spark plug hole of the offending code number one to whatever it is and aim your gooseneck so that it goes in the hole and it's been up a little bit or you bend it up a little bit so you can look up at the head gasket that squeezed between the two surfaces of metal You're looking for water droplets that's what's putting your fire out and causing your missed codes The water is quenching the fire prematurely causing a miss another thing another guy did here and I've done two on one car that this is starting on is take the o-ring out of the d gas bottle put the cat back on tight and don't keep it too too full Make sure it's right on the full mark hot not on the full marker the other Mark cold because then it's going to fill up and squirt out of the overflow hole. On my 2010 solar roof car which is driven for Uber and all that nonsense by my other half that is seemingly stopped the problem temporarily although this is very temporary. She wants to shop for an engine for this car I told her and no one certain terms that's never going to happen she's turned this car into a complete piece of garbage in the 4 years and some change that she's had it damaged all the fender liners screwed up the front fender or front bumper cover so on and so forth it was a beautiful red car now it's getting multicolored plastics or glued back on it she's ran it into the back end of somebody because she thinks she's delivering body parts to hospitals not food the fat people. So I basically told her a generation two is in her life 2008 or 9 and if that's too old to do Uber and all that nonsense with then she'll have to retire because I am not buying or fixing this Prius and this condition for this kind of low no wage nonsense.

 

Start with changing out the spark plugs and swapping the coils around. Then see where you're at.

Have you changed your water pump?

 

If you'd done the EGR cleaning by 100K at the latest, I'd agree.

Most likely head gasket failure is failing, leaking coolant into cylinder(s), at the wall between cylinders one and two (the usual place). Boroscope inspection of the cylinders with the coolant system pressurized, and/or leak-down test, are the usual tests.

 

Toyota sells a "gasket kit" that has the head gasket, plus pretty everything else pliable within the engine. That'd be my pick. Part number for the kit, and head bolts, in the attached.

The kit includes valve seals, which might be best to have a machine shop do. They can do a check of the head. It is extra expense though, getting them involved. If you can get a machinist straight edge and feeler gauges, you check head and block for flatness.

Unless it's been done recently, I'd change the water pump and thermostat, just judging from opinion here.

All the engine related info is in the last attachment in my signature. On a phone turn it landscape to see signature.

 

I found the valve stem oil seals easy enough to replace at home, using the less expensive valve spring compressor from Harbor Freight to remove and reinstall the springs.

A visit to the machine shop might be in order if one wanted to achieve a perfect seal between the valves and the seats in the cylinder head, because they can cut those surfaces precisely. You can get pretty close results at home by lapping the surfaces using either fire-sticks (which are less annoying) or an oscillating attachment mounted to a drill (which provides a smoother finish).

 

It all points to a leaking head gasket....

 

Burning oil is not your driving habits, it’s your low tension rings. Rebuild is the solution if the cylinder walls are not scored.

Shaking and rattling in the middle of the day is end stage hg fail.

The engine won’t do a violent shake and rattle because it’s cold or the egr. Ever. Both are myths. It’s the early (often over many months) and occasional signs of hg fail.

The Parts Cannon is often incorrectly fired at the direction of mechanics and forum members.

A clogged egr will code. A stuck open egr (rare) will continually run bad at low rpm’s. A bad plug or coil will also constantly cause misfires.

A rebuilt engine is the solution.

 

Contrary experience speaking. My Gen 1 began doing occasional violent cold start rattles in 2012 at around 198,000 miles. Never did find a smoking gun in the three more years I had the car before a collision, but there was never any evidence it was HG in that period. The 1NZ in Gen 1 wasn't known for HG problems (and also had no EGR, so it wasn't that either). The main commonality is the hybrid drivetrain, which guarantees a violent loud rattle if the engine is misfiring enough, no matter what is causing the misfiring.

The classic AECS article also has to be remembered as establishing that even minor causes of misfiring are fully capable of causing that violent loud driveline rattle. https://aecs.net/techniek2012/March%20prius.pdf

Also, in Gen 3, the isolated awful rattle, heard only on a cold start if the last engine run was brief and didn't warm up much, is still definitely a thing, happened to me once, and probably is still caused by a snort of condensed water in the EGR passages, as we were told about T-SB-0010-12.

Now in Gen 3, because it seems to be more prone to HG problems, that can justify giving different odds: such a rattly misfire at cold start in a Gen 3 may be highly likely to be HG, taking the base rate of problems into account. But it doesn't justify saying "Won't do a violent shake and rattle ... Ever ... myths" for other causes, when that symptom is known to accompany any serious engine misfire with this drivetrain.

Instead, the timing of the symptom can be used as a clue. Is it constant, or only brief on first start? (Or some other different timing, like only under mid-loads, which correspond to when EGR is active?) Does it happen on most cold starts after sitting overnight? Or only if there was a brief non-warm-up engine run before the cold soak, and never any other time?

If it's only at startup and happening on most cold starts, HG may be a good call. If it's only at startup and never observed except after previous non-warm-up engine run, it's probably the old familiar condensed-water snort.

(It seems like their revised manifold design wasn't much of a silver bullet for the water snort, and that issue is still easiest to avoid just by avoiding those short non-warm-up engine runs.)

 

Periodic EGR cleaning doesn’t hurt either.

 

The condensed-water-snort issue is a little tricky to reason about; I'm not sure whether a sparkly clean or clogged EGR makes that one better, or worse, or samey-samey.

The earliest reports of that issue were showing up on PriusChat by mid-November 2010 early October 2009, probably too early for EGR clogging to have been an issue in any of those cars.

 

EGR clogging > uneven and/or elevated cylinder head temperature > head gasket failure > coolant leaks past head gasket

 

That's a chain of causality you've said a lot about before, and, for whatever it's worth, it applies to issues involving the head gasket.

When discussing any other non-HG, non-EGR cause of engine misfiring, it is flatly irrelevant. And when discussing the condensed-water-snorted-through-EGR-piping cause of misfiring, maybe not as flatly off topic; after all, that syndrome has got something to do with EGR, but still not with EGR clogging; there is simply no way clogging was the issue for the people who were experiencing that issue with their brand-new 2010 cars in October 2009.

It's already agreed that causes of misfiring include failed head gasket as one possibility, and you're already widely on record connecting EGR clogging to that possibility, the one where it has at least a chance of being on the mark. Is that not enough?

 

Burning enough oil to set off the low oil level warning within 5000 miles is certainly not normal. Assuming you want to DIY, you'll be looking to replace the pistons and piston rings with the updated versions.

Updated part numbers:

• Piston: 13101-37240
• Ring set: 13011-37260