Cold-weather startup rattle revisited

Make sure to take note of whether it was fully warmed up before the cold soak and subsequent first start of the day. I can normally make mine do it on command if I start the engine, move the car, shut it off, and not let it run more than a minute or two. The next day it will rattle.


iPhone ?

 

Have you cleaned out the EGR cooler? I am a little concerned, as the start up rattle was blamed on excessive moisture/fuel in the intake... also, Prius with headgaskets failing and ingesting coolant have exhibited the same rattle. You're at the mileage for a potential head gasket problem, based on other owners experiences and stated mileage on this site.

I have owned 4 Pri - A mixture of Gen 2 & 3, and of varying mileage. My 2007 had 217,000 miles when I sold it last month, and was noisy (valvetrain) when started cold. It went away after a minute or two. My 2012 would only "cold start rattle" if I started it up to move it around the driveway, and shut it right off. The next start up would cause a real ruckus. My 2015 does not cold start rattle at all (so far).

 

I've questioned the theory before that the pool of fluid that collects at the bottom of the intake manifold is being sucked into the cyclinders, and causing cold-start-knock. It's just physically impossible. It's a cold, viscous liquid. It can't defy gravity and migrate up the intake runners -- particularly while the throttle is closed and the air flow over the fluid is at its lowest point.

 

Would it be possible for atmospheric condensation within the manifold to cling to the "ceiling" surfaces of the manifold? If so, wouldn't it have a natural path to drain into the intake ports?

 

Is there an assumption at work here, that the goop you're seeing at the bottom of the intake manifold is all there is? Perhaps there's double that amount, all initially airborne mist, and the cold/stable stuff at the bottom of intake manifold is just the portion that condensed?

With an oil catch can in place, that pool is gone for me. There's still a "sheen", but no accumulation.

 

don't feel bad. toyota engineers are still scratching their heads

 

I have a vague hunch (from low-res cross sectional pics of the intake manifolds) that the change (or at least one change) was that the EGR passages went from one long gallery that feeds directly into four capillaries (one per port), to a shorter main gallery, splitting into two intermediate size tunnels, then into four capillaries.

 

Toyota engineers left the room and are working on Gen 5 and Gen 6.

 

On another thread, I am wondering out loud of the solution to this cold start misfire problem is simply a smaller spark plug gap.

 

When I took off the Intake manifold on my 2011, I looked down into the intake valves and there was liquid trapped above all the closed valves


I wonder if that builds up every time you turn off the car.
Then on start up the liquid gets dumped in to the cylinders and causes....

 

Condensation?

 

Valve seals?

Pixel XL ?

 

Could be a mix of
Condensation?
Fuel from the last shot from injectors?
oil blow by?

This is all a guess on my part.
I put a paper towel down there and soaked all of the liquid. I did NOT taste it and it did not have a particular smell that is why I guess a mix.

That car is in excellent condition, I found that liquid when I was cleaning the EGR and Intake manifold
The manifold did have a bout 2 tablespoons of liquid at the bottom (148,000 miles)
Strange but this 2011 never knocks or rattles.
So I don't think that liquid causes rattle or knocks or .....

 

You may have solved an ongoing puzzle. Note that the odds of knock at start up seem to increase, if at the last start up, the car was run only a moment, quickly shut down.

The spring emptying of my oil catch is about half oil, the rest a creamy oleo, mostly water, with a bit of gas?

 

Didn't someone recently mention cleaning their injectors as their fix for a frequent startup rattle?

Would dirty injectors cause them to leak?

 

If they are dirty, they could leak, as they are under constant pressure.
I "think" it was Cosmo Tigato, but not 100% certain of that.
He just rebuilt a motor. He said he had a good spray pattern, which is likely,
but they can still leak if the seat inside is dirty. He cleaned then, and no more knock.

There is a pressurized bottle you can hook up to the fuel rail and pull the relay/fuse for
the fuel pump, then you run the engine until it stops, as the bottle will be empty.
Then replace the fuse/relay. After disconnecting the bottle.
Or you can remove them and use a tool to hook up to the injectors and clean them under pressure.

 

Nope, it was Harry9508 and NickHall834.....
in this thread: Oil Catch Can, Eliminate that knock! | Page 80 | PriusChat
Starting about #1590????

 

Could a catch basin be installed under the manifolds lowest point like a screw in hard bottle?
all the vapor and liquid would just drip down and accumulate in the bottle and not get sucked back up...

This is in addition to a catch can for the PCV

Thoughts... Maybe something we could look into and invent?