Misfire Cylinder 4 P0304

Cleaning the EGR is labor intensive, but while he's in there, he should also clean the intake manifold, throttle body, and replace the PCV. All that is right in the same place.

 

Yeah, the PCV valve. It's super easy to get to with the intake manifold off, but i think it can be replaced without taking off the IM. It's a pretty cheap item, might as well replace it. You'll spend more on brake parts cleaner. I should have put the in the OCC.

 

If you want to save some money, don't replace the coils, that's not a weak link in the misfire chain, the EGR is and because the EGR feeds into the intake manifold, that where more cleaning money should be spent.

 

Replaced ours the first time with the intake manifold on from below .

Definitely a lot easier from above woth the intake manifold off.

And the pcv valve is only ~$7, so we’ll worth it.

 

While this is what everyone has been saying for 40 years... How could such a simple thing like a PCV valve be prone to mechanical failure in such a clean burning fuel efficient vehicle? Is there even one documented instance anywhere on Prius chat or via mechanics where a Pius' engine problem was directly caused by a bad PCV valve? I mean why not just mail me your $7 and I'll buy lottery tickets and if I win I'll buy you a Tesla? Seems like the odds of that happening are higher than the odds of a Prius PCV valve failure...

 

I see your speaking from vast experience here.

While the valve may rattle when you pull it out and shake it, does that mean it is functioning well? How do you measure it?

All I can say is there is oil blow by, which comes from the PCV valve and if the valve is saturated in the vapors, I’d swap it out.

$7 well spent every 100 k miles or so.

 

I'm not speaking from experience, I'm asking a question of those on here with more experience than I...

And yes if there was visible discoloration maybe it'd be wise... But the only time I've ever seen PCV valve that wasn't perfectly clean and functional was in high school when I was working in an auto shop back in the 1980's and those were on really, really old cars with unbelievable sludge problems due to oil leaks and infrequent oil change.

 

On the Gen3 the pcv valve is mounted relatively low, which does promote blow by moreso than on the Gen2 which is mounted on the top of the block. But we don’t have to be as careful when we change the PCV valve, we don’t run the risk of putting a hole in the cover.

Not sure what you mean by visible discoloring, as the valve isn’t visible at all and there is a hose that engulfs the discharge .

Hope that helps .

 

Oh boy....

EGR will NOT cause a misfire due to needing a clean up, wow. Plugs then coils are THE two most likely causes, followed at a great distance by poor fuel atomization by the injectors.

 

They rattle with good springs and broken ones (for those with springs), so that is a no-good test. The PCV valve is the single most UNDER maintained part on most cars, why? No profit in it. They will sell you air filters, brake flushes, cooling flushes, top engine cleaner, and on and on, but almost never a PCV valve. This lowly little part is single-handedly responsible for more oil consumption issues than is imaginable.

The simple solution is to replace it according to the manufacturer's guidelines.

 

Yea... if the misfire isn't related to a blown head gasket, that would be correct... But sometimes people spend way too much time replacing easy stuff before they do a full diagnosis.

 

I saw more than one bad PCV valves in my auto mechanic days back in the 80's on beat up old oil sludge-coated engines, but cars these days run way cleaner and a PCV valve is such a simple basic mechanism that I haven't seen a bad one in decades. So I totally disagree that it is an "UNDER maintained part on most cars." In my book, it's most unnecessarily replaced part because it is so cheap.

Of course I'm always willing to learn... If you can show documentation of lots of Prius diagnosed with a bad PCV valve I'd love to learn more.

 

School in session. How many modern vehicles have you diagnosed with a high oil consumption complaint? I've done HUNDREDS and feel absolutely zero need to document it on this board or anywhere else.

You are welcome to attend the school of hard knocks yourself, if inclined, but those that know because they have done will continue to offer their considered advice.

 

The US maintenance schedule is outlined in a booklet called "Warranty and Maintenance Guide". If you can't find that, you can download a pdf at Toyota Tech Info (just google that), in the "manuals" tab. The spark plugs were not due for replacement at 100K miles, it's 120K miles (or 12 years, whichever comes first). Still overdue obviously, but don't rely on your mechanic to know the maintenance schedule in-and-out, go back to the source.

Don't guess, just top it up to the full line, and keep an eye on it. I'd think if there's a head gasket problem it'll drop pretty fast.

I'd second cleaning the EGR and Intake Manifold, and installing an Oil Catch Can. EGR clogging and the PCV system dumping oil into the intake manifold are a tag-team that enable each other, and once the EGR is clogged your engine temps go up, a lot.

It's possible for a mechanic to do all this stuff, but it is labour intensive, which means either he'll cut corners, or it will cost you a lot. Your best bet for all of this is to DIY. Some threads:

EGR & Intake Manifold Clean Results | PriusChat

Oil Catch Can, Eliminate that knock! | PriusChat

And for invaluable videos, by @NutzAboutBolts :

Nutz About Bolts Prius Maintenance Videos | PriusChat

 

Yes, I love school... Learning is my greatest obsession! Can you send a link / explain how excessive oil consumption symptoms are PCV valve related? Especially as relates to Atkinson combustion cycle on a Prius when PCV valve shows no discoloration or malfunction when you inspect it?

Also is Atkinson more prone or less prone to PCV valve issues?

You don't have to spend much time on this... Just please point me in the direction of learning more?

 

Absolutely...

NOT.

Educate yourself.

I will not argue with those who insist that what you read from a g00gle search or watched on yourtoobe is accurate. Much of what separates the great mechanics from the parts changers is experience and the willingness to learn.