Death Rattle

From post #7,

No additional maintenance is required other than what you already are doing.

The "death rattle" has happened to me two separate times over the last 5 years. One time it happened the day after there was a light mist in the air when I turned the car off. The next morning, I had about 12 seconds of misfires (death rattle) when I started up the car.

The second time was when we had a couple of cool, high humidity days. That night, I turned the car off, and the next morning, I had a brief time when the engine misfired.

So it will occasionally happen. It scares the heck out of you when it happens, but there's not much you can do about it besides making sure the car is completely warmed up when you turn the car off for the night.

 

It's NOT likely that the head gasket has failed. It is possible, but NOT likely.
Maybe the engine was hot, then shut off, and it's a lot cooler outside.
Condensation could form in the intake manifold and/or cylinders. Then you'll get that knocking.
The next time the engine starts.

And since you said it only happened once, it is possible that is the issue.

Orrrr, if you didn't let the engine fully warm up, but only let it run for a few seconds, because
you only moved the car, then shutit off, you could have extra fuel in the cylinders that hasn't
gotten burned. Which will also cause the knock... The next time the engine starts.

 

report your post and ask the mod

 

Are you by chance posting on an iphone? If so, Priuschat has a bug: if you edit your post more than once, the site serves up the old version, pre-edit. Every time you make a move you need to reload the page, or it's a disaster.

Repeatedly reported, nobody appears to be home...

 

As stated before, having one rattle six months ago and never again is nothing to worry about.

The dealers DO know about head gasket problems and they know the signs and symptoms. You are ok and likely have years to go before any major expense happens.

There really isn't any clear cut absolute preventative maintenance you can do other than change the oil and coolant twice as much as the book recommends.

 

The EGR Cooler will always have some crud in it.
But it would only slow the overall EGR flow to the intake.
If it limits it enough the car should show a Code from the MAP sensor not seeing what's expected due to low flow of EGR.
I don't know what that code is.

Some here think that the Uneven flow of EGR to the individual cylinders is what causes the HG to fail in the #1 or 2 cylinders.
The very small EGR ports going to each cylinder get clogged unevenly, due to the hot gasses having more time to cool and condense out the crud, more so in the farthest ports than the closest to the EGR entering the intake manifold. Just another SWAG....

These ports can be quickly cleaned with small rotary brass brushes on a drill and cleaning solutions.
There would be no reason to buy a completely new intake manifold. (unless you work at a dealership and they like selling parts).