2010 Prius Knocking (Raptor Sound)

Thank you very much for input Kortenbach

* Actually cylinder #1 is the farthest from the EGR.

The layout is left to right: 1, 2, 3, 4 <- EGR Pipe​

The problem is not limited to low RPMs it also happens at higher RPM's:

Originally the problem was intermittent. I only had the problem while driving under certain loads…. normally at low speeds with heavy loads (going up hill with low to medium acceleration). Also occurring for short times when letting off the accelerator. Never occurring at moderate to heavy acceleration. Never at idle.​

The problem has not progressed to a point where it happens every time when the HV charging kicks in when the car is stationary. This is why I am performing all the benchmarks in the maintenance mode at idle speeds. This environment simplifies the issue and remove a lot of the other variables. The problem it replicated like clock work when the HV charging occurs.​

I am suspicious of the EGR valve and I have the blocking plate on my to-do list… lately I have been wondering if the valve is not closing properly and causing the problem when manifold pressure is increased (hence the HV charging). Perhaps the hissing sound is also caused by the exhaust gasses passing through this leakage.

I don’t understand why it’s only causing the misfires on cylinder #1... but I still think it may be a plausible case for the problem.

 

Thanks again for our valuable input...
I tried swapping the coil earlier, no change, then I tried 3 new coils, then I swapped all 4 coils and spark plugs with Prius #2... no change.

Thanks for the feedback... I checked the PCV valve when I rechecked the intake manifold a few weeks ago. It seemed ok to me... Didn't look clogged, only passed air one way when I manually blew into it...

Wow... thanks for posting.

From the picture it looks like the head gasket it missing between the #3 and #4 cylinders (the two on the right hand side - looking toward the rear of the car)... it that correct?

Was the source of the problem excessive temperature?
Did the car overheat from the clogged radiator?

mindfk - Thank you very much for you valuable feedback... Really appreciate the help on this one!

LTFT - Excellent question...Originally it was quite high... 18 while idling, 23 under load.
The STFT generally has level around 0 so it seems to be happy with this adjustment.

Once I discovered this I thought for sure it was an intake leak... That would explain the hissing and the noise with misfiring. However I could not an intake leak using the normal techniques (propane/spraying carb cleaner near the hoses and intake manifold, etc.).

I moved on to the injectors... once I swapped them with the other Prius, the LTFT was back to a normal range (~4.5).

The interesting thing is... The high LTFT did not generate a check engine code.
I would have though this was excessive but apparently it still stays inside the acceptable margin.

EGR Plate - Good Suggestion.
I've thought about making a EGR blocking plate from a piece of sheet metal (similar to your picture) but just never took the time.

I kind of stopped worrying about the EGR valve when the problem starting happening at idle speeds (1100rpms in the maintenance mode).
I assumed the EGR would always be closed at this speed. Techstream shows the Target EGR Position and the EGR Step Position at 0% before and during the problem condition.

I also wonder this could be a problem where it is not closing properly and allowing gasses to flow when it's suppose to be closed..
.It does create a similar effect if I open the EGR valve in the test mode... but I believe this is normal.

Do you think I should pursue the blocking plate?

As you might expect... I can also create a similar condition if I vary the VVT control valve. I have suspicions that this could be the problem area but it had not affect when I swapped it out with the other car.

I can't help but wonder if there is air or oil passage that is partially blocked that is causing the problem (similar to carbon in the intake manifold)???

On the stethoscope... we tried that. I had three different mechanics try to find this sound… we all had no luck. One of them used a stethoscope very similar to the one in your post. Right now the hissing sound is simply not present.

Thanks for chiming in Juba79

I'm not sure I totally understand you post...

I think you are saying that you have or had a Prius with similar symptoms and the car was fixed by doing a head job or replacing the engine?
.
Did you mean that?
A. A bad head gasket was the cause and resolution to the problem?
or
B. The problem was present and it continued until the engine failed with a blown head gasket?

Can you expand on the problem(s) that you discovered?
Can you tell me more about the location of the leak?
What tests were done to location the problem?

Did you get water in the block or see exhaust leaking from the head, etc.

Is there anything unique about a Taxi application that would cause this failure?

Again thanks for your valuable input in the problem.

 

Update 10-22-15 The #1 Cylinder Misfires Counts shown in Techstream and reported 10-16-15 have now disappeared.

10-15-15 Review:

The tests were performed when the car was in the maintenance mode (where it continues to run at about 1100 rpm).

The car will start/stop the knocking sound in concert with the start/stopping of the HV battery charge state. Each and every time the charging mode starts and stops the knocking starts and stops. The engine load increases from about 30 to 60% when the charging is in play.

About two weeks ago the car was showing constant "misfires counts" on cylinder #1 during this condition (as view in Techstream).

The misfire counts where only in cylinder #1 and only during the HV Charging / Knocking condition. The counts would increment from 0 to 99, back to 0 then back up to 99 in this consistent pattern. (See the Techstream database file and screen shots in post #20).

Once the HV charging stopped the misfire counts stopped and magically reset to 0. The check engine light never came active... (nor did any pending check engine codes).​

* On Monday 10-19-15 I removed the EGR pipe and EGR valve.

It's hard to say for sure but it's possible the EGR valve was slightly open.
I say this because once I took it apart it seemed like the mechanism was not fully closed. However that may be just the way the stepper motor rests when it's not under EGR control.

​

Cleaning the valve and the EGR pipe did not fix the problem. The valve definitely had soot in and around the seating area but it was not terribly gummy like the intake manifold. In general both the valve and pipe were dirty but not overwhelming.

It's been about two weeks since I worked on it. During the 10-3-15 set of tests, the hissing was not present...

During the 10-19-15 set of test, thee hissing is somewhat back and the consistent cylinder #1 counts are no longer present.

There are some misfire counts but not just on cylinder 1 and not as many as measured with Techstream a few weeks back when those were performed.

Why are these symptoms changing ???

10-22-15, I ran addition tests... This time focusing on the EGR valve. I wanted to confirm it was staying closed during the maintenance test.

I removed the EGR stepper motor control so I could manually open and close the valve. Judging from the temperature of the EGR to intake manifold pipe it appears that the valve is closing properly as the pipe was cold when closed and warmer when open.

Performing a slight opening did not reproduce the hissing sounds but did affect the knocking (as expected).

When the HV charging switched on, the raptor sound started as expected. At this point I could manually adjust the EGR opening to make the engine run correctly. This is similar to when I made the adjustments via the Techstream active data test but this time I was able to make the adjustment in a more refined responsive way and it was close to normal... but I had to continuously adjust the valve in a dynamic situation.​

I also played with the PVC and the Evap tubes. Both had a high vacuum presence and both would make the engine stall if I disconnected the tube for more than a few seconds.

Any help is very much appreciated...

One though came to mind when I was working near the ERG valve...

The knocking sound appeared to be coming from the transaxle area.

It reminded me of this video I had seen on youtube that identified the knocking sound as originating from transaxle:

Gen 2 Prius Misfire

"When Prius misfire the planetary gearset in the transmission slaps around, which can sound like a rod knock. This car had a clogged injector at cylinder #1, and that is all."

It made me think...
* Could my problem be in the transaxle?
* Could this area be imposing a varying load that is causing the engine to misfire?
* Perhaps there are no misfires... the problem / knocking sound is coming from a problem in the transaxle?

This problem is driving me nuts...

* Compression Test: Not yet... it's on my todo list. I have to borrow the tool.

* Seafoam Test - I'd like to do this but I have a few concerns.

A. The car is already making a deadly knocking sound... I'm concerned about driving it for extended time periods in its current condition.

B. I can get to 2500 RPMs while parked in the maintenance mode... is 2500 close enough?

C. I can't think of a way to get the engine to run at even higher rpms for an hour after the cleaning procedure.​

Has anyone tried this on a Prius?

Hills are hard to find in the Dallas area...

Good idea... I hadn't thought of the camera trick.

Can you post the url to the facebook pages?