Advice Needed! P0401, P0300, P0301, P0303 Head Gasket and/or EGR?

^ worth noting.

AFAIK NGK were never the stock-from-factory plug. Previous owner replaced, possibly counterfeits?

I’d still be on alert regarding the head gasket.

 

QUOTE="ALTEREG0, post: 3474569, member: 215215"]Actually, it was me. I just replaced the spark plugs around 3 weeks ago with a set I bought online.[/QUOTE]
That's a revelation lol. Was that just before the symptoms/codes started? The plugs could well be the cause of the shake-on-startup. I would take it as wake-up call. Your EGR will be clogged, guaranteed with the miles, and head gaskets have blown well before those miles. Just keep an eye on the coolant level, get on that EGR cleaning as soon as you can manage.

For sure get a set of Denso's, preferably from dealership; latest has the number 16 instead of 20.

 

Latest Denso part no is Denso SC16HR11 (used to be SC20HR11, per owner's manual, but revision is a slightly hotter plug)
Toyota assigns it part no 90919-01275

 

I wouldn't sweat oil catch can for now; it can be a bit of a rabbit hole. I've got a couple of Moroso 85474 air/oil separators (basically the same thing), in series, mounted on as bracket* atop the lower front beam, below the intake manifold. That location was a bear to deal with, and with two cans it JUST all fits, not touching the (sprung) engine or associated stuff.

The Moroso 85474 have gotten crazy expensive, food for thought. They are a very solid product though, you'll need to put them in your will, lol.

One gotcha with them: they have a large/thin o-ring at the seam around the midriff of the barrel. After opening/reassembling it a few times that o-ring stretched badly. I contacted Moroso for info, and these are the specs for the O-ring, plus they recommend to always lube it with anti-seize:

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O-ring info from Moroso:

We do not list a replacement o-ring for that, but we do have them in our warehouse. You would need to call us direct if you wanted to get one ordered, or you can source an o-ring with the same specs; 2.614" I.D., .070" thick in Buna-N. What you saw on the threads of the catch can was anti-seize, we would recommend applying more to keep the top and bottom halves from seizing together over time. It is possible the o-ring was stretched or pinched upon reinstallation.


Brett Corriveau
Sales Support Technician
Moroso Performance Products
80 Carter Drive
Guilford, CT 06437
203-453-6571 x332
[email protected]

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2.614" I.D., .070" thick in Buna-N
(66.40 mm I.D., 1.78 mm thick)

The above spec is like O-Ring "dash" number: -038

Search strings:

O-ring -038 Buna-N

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Moroso 84574 Air-Oil Separator O-Ring:
Oil-Resistant Buna-N
Dash Number: 038
(Relube with anti-seize periodically)
2.614" I.D., .070" thick in Buna-N
(66.40 mm I.D., 1.78 mm thick)
-------------------------------------
Steel mesh biscuit part no: 85472059
(only available by direct order from Moroso, $5 USD apiece)
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I was able to get those o-rings locally, had to buy maybe 10 of them for $20.

* The OCC bracket atop the beam should be "loosely" mounted, says with a rubber gasket between it and the beam, with hold-down fasteners finger-tight-and-locked: the underside of that beam is the front jacking point, and it needs to flex.

 

The fact that plug got that gummed up in three weeks is not great. But I would drive it frequently and watch for more shaking in the next three weeks. Which happens to be the interval new plugs clear the shaking on a hg leak. Realize the shaking does not occur if the plugs fire. Bad plug misfires and shakes are continuous while coolant fouling is short term as the engine starts or restarts with an advanced case while driving.

In the past many people have temporarily cleared shaking with new or even cleaned plugs. Watch the coolant level as well but shaking is the first symptom.