Knocking and rattling noise on low speed 2012 prius

When you had your manifold off for cleaning, did you replace the PCV valve? A malfunctioning PCV valve could be the cause of the rough running at idle/low speed if it's stuck open, letting in crankcase vapors and loosing vacuum, which affects low rpm performance more than higher rpm performance, when the valve would be open anyway.

Posted via the PriusChat mobile app.

 

No video but if it sounds like this it is likely a head gasket since you have replaced the other parts.

 

How many miles on it?

If 150,000 miles or more, and the Exhaust Gas Recirculation circuit and intake manifold has never been cleaned, I too would suspect head gasket failing. This is happening regularly with 3rd gen Prius (like yours), and very often it's at cylinder one, sometimes cylinder two.

A leak-down test would help immeasurably, to diagnose determine head gasket condition, and pinpoint where-and-how if it is leaking.

More info about EGR cleaning in link in my signature.

 

Many people have the same initial response and it turns out to be the head gasket. The coolant leaks small amounts at first and exhaust gasses replace it. Driving like this will make things worse including engine replacement. Other missfire sources like plugs, coil, injectors or stuck open egrs (not clogged) will not quickly clear up and will last long enough to throw codes. A borescope analysis is often definitive as the leaking cylinder will be cleaner than the rest.

Denial is the first stage of acceptance. In this stage, individuals believe the diagnosis is somehow mistaken, and cling to a false, preferable reality.

 

Hmmmm.

 

Have the same issue, no codes. cleaned the intake manifold,
Cleaned the egr valve
Cleaned the cooler
All three items were not to badly clogged.
Changed the pcv valve
I did find I piece of the metal catalytic shield loose and it came off, that helped some what but still vibrating at low speed only
I also changed all four plugs
Can someone chalk the pics of the cylinder shaft and tell me what you think
My last resort is to change the injectors

 

How many miles?

 

150k,
Today the noise got louder when going slow in heavy traffic.

 

Yup, same issue here with my 2013 with 134000 miles. Ended up being the head gasket.