Oil Catch Can, Eliminate that knock!

That'd snarl up the two-way traffic. The valve-cover vent is filtered air from the air cleaner being admitted into the crankcase in order to help flush blowby gases out through the PCV hose.

The only exception is under WOT conditions, when the vacuum difference between the two ports is so small that, just during those conditions, flow in the breather hose reverses so both hoses then flow from the crankcase.

-Chap

 

This is good stuff, Dan.

My car developed a hesitation the last several weeks at 168k miles that I knew was misfiring. A week ago, it got worse during a local drive, and the check engine light came on for Cylinder 3 misfire. I parked the car at home until I had time to pull off the intake manifold. Meanwhile, I gave myself a scare by thinking that my coolant level was down - misfiring coinciding with losing coolant = blown head gasket. Thank goodness I was just seeing the difference between the cold coolant level, which I don't usually see, with the warm coolant level that I usually notice when I check fluid levels at every gasoline fill up. I had already gotten a quote for head gasket replacement from Luscious (though I'm no longer close enough to visit them) to compare with local places/the dealer, and it was $7000+ including a new short block, which they said they typically recommended.

When I took the intake manifold off the other night, there was enough oil below the throttle body that it totally soaked a sheet of paper towel - two tablespoons at minimum. The oil was wetting everything in there, including the entrances in the head. I had last cleaned the intake manifold 17k miles ago, so that's how much accumulated in 17k miles. There was minimal soot and sludge in the EGR passages because of that cleaning 17k miles ago. I also had a new EGR valve from the enhanced warranty (for insufficient EGR flow P0401 and associated misfiring) about 10k ago. There was less than 1 mm of new soot buildup in the EGR pipe. There was some oil, but no sludge in the tubing between the PCV valve and the intake manifold. That tube was sludgier 17k miles ago (when I also replaced the PCV valve). I'm convinced the oil is from the PCV valve.

I was a bit apprehensive starting the car up today after putting things back together last night. If I really had an internal coolant leak, the misfiring might be worse if a head gasket leak was accelerating, like I was worried was a possibility after the last drive. I had thoughts of hydro lock after reading Dan's other thread. But it started up and ran pretty smoothly - better than it had since I started noticing hesitation several weeks ago. Though I noticed some questionable instances of hesitation, it might be some residual oil that I couldn't reach when I was cleaning. We'll see. The only thing that I really accomplished by taking off the intake this time besides inspection was to was clean oil out of it, so oil sitting in the intake manifold getting blown into the combustion chamber(s) was likely the cause of the misfiring.

I'm going to order that Ruien OCC from Amazon (saw Dan's review of it there). Too bad I didn't have it on hand already, because I'll have to take things apart again to reach the PCV valve.

Any ideas for how to mount the OCC? Like most people, I don't have a 3D printer. I'll probably end up improvising with zip ties.

There's not much room at the U-shape hose. There's the vacuum switching valve and mount there, and coolant hoses going to the throttle body, and a larger coolant hose below that. But maybe you could route the hoses further down to the subframe by the engine mount there?

 

I live in Alaska, but I bought the car in California last year. The past winter was its first in Alaska. The car is garaged (45 F minimum, 55 F typical in the garage in the winter). Away from home in the winter, it is sometimes parked in the cold for 2-4 hours at a time. It has never had cold start knocking.

There was no white residue below the throttle body. It looked like all oil.

When the hesitation happens, the engine keeps running, but I feel and hear an interruption in power. Stuttering is another good descriptor for what happens. When the car has it, the hesitation can happen at any throttle position - from idle to high. Typically, when it has happened, I soft foot the gas pedal to go to EV to try to interrupt it as much as possible, and go easy the rest of the way home. I once tried more power during a hesitation because that works for some people in the some of the knocking threads, but it didn't stop the hesitation. I don't know if the knocking in those threads are misfires. I know the hesitation that I have experienced in my car has been misfires because misfire codes pop up eventually.

 

@Lightning Racer just curious: do you have the block heater?

 

No

 

I wonder if most of the oil in the intake problems are caused by the common issue of dealers overfilling the crankcase. Crankcase needs an odd number of quarts (4.2 if I recall) and I've read reports of dealers just adding 5 quarts at an oil change. With the PCV valve so low on the engine this could cause the oil-in-the-PCV problem. Even if the oil level does not reach the PCV with the extra 0.8 quart when the engine is cold, there will be frothing and foaming oil when the engine is ran - raising the level. Forcing the engine to burn oil will cause the rings to stick which will exacerbate the EGR system and start the whole cascade of problems...

 

For the 17k mile period in my car that I described several posts up, where at least 2 tablespoons accumulated, it hasn't been over filled. I check the level every fill up (and after an oil change to verify).

 

Are you sure that will work?
Venting from the valve cover is above the pistons. They already have pressure relief through the valves. The bottom of the crankcase. Holds pressure from below the pistons. I think if you seal off the bottom of the crankcase and vent only from the top, you will build up pressure inside the crankcase which can crack it.

Or am I missing something? I admit that you've torn this engine down and I haven't, so you have a much better visual understanding than I do.

 

Back a few decades PCV valves were just plugged into a rubber grommet in the valve cover, were they not? Maybe they were not as effective thus? I know I replaced a PCV valve on an 06 Civic recently, and it was a similar pain, below the intake manifold.

 

I ordered this one/

same as the ruien/

one HAS to remove the intake manifold or is there a different way to reach the short hose at the pcv valve?

 

@NutzAboutBolts video, pinned in Maintenance Sub-Forum: he removes PCV valve from below, unclipping and shifting a hybrid circuit cable for better access.

 

Ok, I see now. But I assume you would keep the OCC, because the oil can exit the engine as a vapor.

 

Here's an update. The misfiring continues after cleaning the oil out of the intake. I guess that makes sense, because lower mileage cars also have oil in the intake, and they mostly don't misfire even though they are probably combusting some of that oil after about 20k miles.

I pulled out the wiper tray and cowl (not too bad a chore, removal took 24 minutes using hand tools, my first time) and checked spark plug #3, where the misfire was occurring. The spark plugs had been changed at 151k miles (only 17k miles ago) by Luscious Garage using the original Denso SC20HR11. The spark plug was not fouled, and looked OK to me. The gap measured 1.0 mm, which is in spec (1.0-1.1 mm new, max 1.3 mm). I swapped it with the spark plug in cylinder 1 (gap was a bit under at 0.975 mm... close enough I guess - not supposed to adjust them?). I also swapped the coil from cylinder 3 with the one in cylinder 2. I then cleared the check engine code.

Today, the misfire is P0301, so the misfire followed the spark plug to Cylinder 1. I'll either change that one plug, or just swap out all 4 again. Looking at old threads, it looked like maybe the spark plug was superseded by a hotter plug, the Denso SC16HR11, but I couldn't verify that. I did see interest in the threads for the Denso Iridium TT. I looked that up, and the one that fits the 3rd Gen Prius (IXEH20TT) is only $7 on Amazon, so I might go that way.

Here's a question for you guys. The misfires that knock are detonations, right? So those are bad, and can damage the engine and head gasket. How about the quiet hesitation misfires that I've experienced? Are they likely harmless long term? I'm asking because I'm considering selling my car after fixing the misfire problem, due to fear of head gasket failure.

A head gasket failure would cost way more than any gas I would save with this car. In fact, my first choices when shopping last time were Subarus (I have a reliable old one, not prone to head gasket failure with the EJ22 engine), but I was put off by potential for head gasket issues for the used ones that I was looking at. At least they cost less to fix than an engine swap or head gasket repair on the Prius. On the other hand, if my Prius, which has had good care, is likely to go 300K miles, I'll keep it.

 

I'll adjust the gaps when I go in again, but the plug that was misfiring was in spec at 1.0 mm. I was hesitant to adjust the gap in the other one because it wasn't misfiring and I remembered comments in previous threads that said not to adjust the gap. I'm not sure what the reasoning was. Maybe to not scratch up the tips? Carefully wedging them open slightly wider shouldn't damage anything.

I haven't cleaned/flushed the fuel injectors. But I do have Techron in the current tank, and I also ran Techron in a tank about 10k miles ago. I have been using Top Tier gasoline. I'll look into the fuel injectors next if the spark plug doesn't fix the misfire. I watched some fuel injector testing videos on Youtube last night. Learned about listening to them with a screwdriver, and some other things.

The EGR valve was new from about 10k miles ago. It was fixed under the enhanced warranty for P0401, insufficient EGR flow. I think they cleaned the EGR cooler then too, though I'm not sure. That EGR replacement fixed the previous misfiring the car had experienced after popping that P0401, and it had been good again until now. The EGR pipe and ports in the intake are 100% clean as of last week.

All the used Subarus I looked at before buying the Prius were suspect for head gaskets. The turbo Subarus don't have head gasket issues, but are even risker used... lots of blown motors, and cars driven really hard. If I can find a nice ~100K mile 2007 Legacy or Outback wagon with the head gasket already replaced, I might sell the Prius for it. My 1996 Subaru is nicer to drive in terms of handling than the Prius... too bad it's rusting and has had the dash chewed up by my GF's dog. I like Hondas too, though they haven't had a wagon or hatchback (on the used market) the size of a Prius or larger in a while. Maybe the Fit is big enough for me though. Too bad you can't do engine swaps easily in the Prius. It's amazing the engine swaps you can do to a Civic or Insight. Here's an Insight with a 438 WHP and AWD:

 

The answer is no. The only reason misfire sounds like a knock in Prius is due to electric motors kicking in in the instance of misfire.

You
should be able to test spark plugs with good multimeter. There should be infinite resistance in the MegaOhm range. My experience is fancy iridium plugs are irreversibly damaged when flooded and register 1-2 MOhm despite cleaning. It happened to me many times in my boat before I wised up and put old OEM copper plugs in.


Sounds like you should do the EGR cooler cleaning. Doubt dealer did that for you. They don't clean, they swap parts.