Death Rattle... clean manifold & EGR, new plugs, no change

Try putting the old plugs back in? Where'd you get the new ones?

 

Damper between engine and transaxle has damaged springs? There’s a plastic panel at the junction I believe you can pop out, see if there’s spring fragments or whatever.

 

I reread your first post and you noted a couple of things:

Daughter's daily driver.
You were going to originally inspect the engine and exhaust mounts?

At this point I would stop and ask your daughter if she noticed anything, or if anything in her driving around may have caused this...

REVVL V+ 5G ?

 

Looks like you're just varying the amount of load put on the engine. Keep in mind that the way the transmission works, 72% of the engine torque takes the mechanical path to the final drive at all times. When the battery needs charging and you are comfortably sitting in Park, the HV ECU knows it can ask for plenty of engine power for charging and the car won't roll, because of the parking pawl. In D with your foot on the brake, it is more likely to limit power to near idle, so you will have a smooth take-off when you release the brake. This is probably the same in P with the foot brake, because the foot brake is probably taken to suggest that you might shift soon and do something.

The key is that, as the AECS paper explained, the sound is what a misfiring Prius sounds like. When people say it sounds like a head gasket, that's because coolant leaking in a head gasket case causes misfiring, and misfiring sounds like that. So does misfiring for any other reason.

Though damage to the springs in the damper can make the sound even worse, if there is such damage, misfiring is likely how it came about.

 

You can find more about the misfire margin and other tools for misfire diagnosis in the Second Quarter 2009 issue of Toyota Tech (starting on page 15).

The margin is kind of a sliding scale. Negative numbers are bad news ("in the negative zone, a misfire is occurring"). Positive but under +30 is still "a high likelihood that a misfire is occurring." The farther above +30, the less likely. The scale doesn't stop at +100; mine was something like +134 last time I looked.

 

Boy, "turd gen" at it's finest...

Consider an hour of dealership diagnosis? Maybe they can even talk to Toyota USA; that's nuts. And at 127K.

 

Not in the case of a gen3 Prius with erratic engine rpm. The mg transaxle has to maintain sync with the engine perfectly. When it does not, for a variety of reasons, the spring loaded damper makes the death rattle. Every time. Usually its a coolant caused misfire (common) but could be ten other conventional ICE issues like timing, fuel, control or sensors.

Red herring?

Does "roughness" mean engine rattling? Smooth when closed is a clue since the egr should be closed at low speeds and wide open throttle.

This may be a quote for Grit's signature given the symptoms. It seems it is not running properly. Hopefully I am wrong and its a unicorn issue like a very unusual inverter problem (since codes and limp mode are typical) or the rare flying unicorn, eg a bad damper. I believe johnnychimpo replaced his after his gen4 engine into a 3gen car swap.

 

On first listen that sounds like a faster rattle than my memory of misfire rattles, but I guess not by much.

There might be some insight to be had by loading that audio into something like Audacity and using a ruler on the waveform display to find the actual time between the individual clacks making up the rattle. You could compare that to the known RPM of the rotating bits.

The engine idle target RPM is 1000, or about 16.7 revs/second. So anything happening once per engine rev (or every two power strokes) will be happening 16.7 times a second. Anything happening that's connected with one particular cylinder's power stroke will be happening around 8.3 times a second. (Something happening with every power stroke would clock in at 33 times a second.)

When you're parked, the only other thing turning is MG1. From the nomograph, we see at zero road speed and 1000 engine RPM, MG1 is turning around 3600 RPM, or 60 revs/second. That's up into the audible-pitch range; anything that was associated with revs of MG1 itself would not really sound like a rattle at that speed, more like a deep B♭, same as North American power line hum. Anything associated with balls in the tranny bearings, or the poles of MG1, will be even higher frequencies than that. By process of elimination, I'd still say we're hearing something that goes with engine rotation.

 

Not sure I did that right, but looks like roughly 30 pulses in a couple of seconds, so about 900 per minute: which is in ballpark for Prius idle speed.


The attached .zip file contains the mp3, the video's audio.

 

Given the extreme precision involved in eyeballing an Audacity screenshot, I'd say 900ish or 1100ish would qualify for a "yup, looks like engine RPM."

If the rattle consists of clack pairs (free play being taken out forward, then backward), those would be happening at half engine RPM, same as any single cylinder's power stroke.

 

I’ll fall back on this, from page 2:

 

Keep in mind that MG1 turns at a markedly different RPM than the engine (except for particular moments in driving when the line across the nomograph happens to be flat). That's why it was interesting to analyze the sound for whether it matches up with engine RPM or with MG1 RPM.

 

To quell @Mendel Leisk 's concern have you checked for exhaust in the coolant?

IF you believe it is MG1. Is this an actual rare case of it failing? And if so, what fluid is in there and for how long?

REVVL V+ 5G ?