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What To Do With A Generation 2 Toyota Prius Mysterious Engine Knock

Is your Prius making a rattling/knocking noise? Or are you suffering from poor fuel economy and reduced power? Tune in to see what could be causing this issue. Hint: It is not your hybrid battery.

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Full disclosure here this is an article based around studying and theory. The follow up to this article will be a full scale detailed repair and what it took to get there.

This article is going to cover what the issue is that we are dealing with and what I think can solve the problem. We will be including Generation 2 Prius (2004-2009), which utilizes the 1NZ-FXE 1.5L gasoline engine. This engine also found in Prius C and Generation 1 Prius. I am currently unaware of this issue plaguing those models and years, so we will focus on Gen 2.

What Is The Issue With Gen 2 Prius?
Recently I have had two second-gen Prius come into my life with an extraordinary issue. The problem is that the engine sounds like it has a "rod knock," referring that the connecting rod bearing clearance is too excessive, causing the connecting rod to slam against the crankshaft, thus causing the noise.

The interesting thing about a rod knock is the noise will be consistent and change speed with RPM. This particular noise will go away at higher engine RPM, which makes me question what is causing the noise?

I have a theory, backed by a trouble code, and information from Toyota on what the issue could be and how to fix it. For now, know that this is not a fluke issue. It happens, and I now have two confirmed cases.

How To Fix The Knock/Rattle Issue, Theoretically
As I was making the arduous 12-hour journey back from an undisclosed location with my new-to-me 2007 Prius, it suddenly lost a lot of power, and the car set a trouble code. As any good Prius owner would, I whipped out my trusty OBD2 Bluetooth adapter and plugged in.

After booting up Dr. Prius, the trouble code reveled a P0011 Camshaft Position "A" Timing-Over Advanced or System Performance. Okay, so what could be causing this issue. Looking into it, Toyota states four main areas can cause this trouble.

Area number one, Camshaft timing gear assembly, or the VVTi timing gear. Area two, the oil control valve or VVTi control valve that goes to the camshaft gear. Area three, the valve timing itself and area four, the Engine Control Module or ECM.

Thinking logically, I doubt the ECM is going to be the issue on Prius. I would not rule it out, but I am also not going to jump to any conclusions. Valve timing, I could see if the engine had a ton of miles on and the chain was stretched, but again, this is a Prius we are talking about, a stretched chain would not be my first plan of attack.

The other two components share something in common. They are both units that work with oil. The VVTi cam gear relies on the VVTi solenoid to feed it clean oil to it. The oil pressure will allow the camshaft to advance or retard engine timing based on the demand.

Toyota Prius Oil Control Valve Filter

So, what if over time the owner missed an oil change or two? Or maybe the owner used a junk oil filter, or went way over on oil changes? What would happen then? Do you think we could see some sludge and debris buildup inside the engine? Chances are this is exactly what could happen.

Then what? Well, what if the debris was caught in the tiny ports, holes, or somewhere else that prevented good oil flow to the VVTi cam gear? Do you think we would have a driveability issue? Absolutely.

My theory is this, take a look at this picture courtesy of Toyota Motor North America. It shows a picture of an oil control valve filter. What if all we needed to do was clean out this filter and restore oil pressure to the VVTi cam gear and allow it to move as it should?

Toyota Prius Oil Control Valve Filter Screen

In theory, this all sounds like it should work 100% and solve the issue. I will be conducting this experiment in a couple of weeks after I return home to see if this is the problem. Until then, if you have the death rattle on your Gen 2 Prius, clean this screen and let me know if it solved your problem.

Thank you, everyone, for reading. I look forward to helping you further in the next story. Will The Hybrid Toyota Venza Be The Replacement Prius V?

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Peter Neilson is an automotive consultant specializing in electric cars and hybrid battery technologies. He holds a Bachelor of Science in Automotive Service Technology from Weber State University. Peter is also an Instructor of Automotive Technology at Columbia Basin College. Peter can be reached on Linkedin and you can tweet him at The_hybrid_guy on Twitter. Find his page on Facebook at Certified Auto Consulting. Read more of Peter's stories at Toyota news coverage on Torque News. Search Toyota Prius Torque News for more in depth Prius coverage from our reporters.

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Matthew Nunley (not verified)    November 11, 2020 - 7:10PM

Did you resolve your issue? Mine makes similar knock "tack tack tack" especially under load at ile while recharging. Plugs ,coils, fuel cleaner, vvt gear ,timing chain, tensioner, valve adjustment, water pump and still there. I know its not rod knock bcause its been an entire year now. Im considering injector misfiring or cvt transaxle damper assy clacking ive given up spending any more time at this point

Richard (not verified)    August 2, 2021 - 7:28PM

In reply to by Matthew Nunley (not verified)

Having the same issue. Dealer said it was a bad head gasket. Rebuilt the head replaced VVT & screen. Still made the noise. Pulled the bottom and the lower end and all bearings are fine. Didn't find anything wrong with connecting rods.

Any idea what's wrong?

Tracy Richardson (not verified)    January 5, 2022 - 9:24PM

I have an 08 Prius, I replaced the fuel injectors to find out that 2 of them were bad. The car threw codes that cylinder 1 and 3 were misfire. I took them out and put the old ones back in, but now the car is ticking. It gets louder and faster when the motor is reved up. Can anyone help me?