Horrible racked noise at start up

Seems like the knocking is caused by moisture, ie when you start the car to move it and shut it off then without letting it warm up. The next time, the water that's collected in the intake makes it sound like a diesel. That's my theory anyway. Otherwise, why would Toyota redesign the intake? And every time I've gotten the noise, it was from that exact scenario


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The current theory is condensation & oil. Those liquids do not compress as well as the fuel, creating the knock

 

I don't understand why oil would have anything to do with it unless it's coming from blowby from worn piston rings


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From PCV valve, I believe

 

Ahh, I see. Again, IMO shouldn't be a problem unless there is excessive blow-by. I guess it combines with the moisture though and ends up being one and the same fluid.


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I have not cleaned the egr system at all on our 2010 prius and have had an occ in place since 80k with 117k currently. The 2011 has had a rebuilt engine with complete egr system, intake plenum cleaning and occ done since 297k with 306k currently. Both cars run smooth. Both prius' trap more water in the winter with a small mix of oil and fuel in the occ. In the warmer weather I see more oil. Either way I see it, I do not want any of this contaminant in the intake plenum. I do not think it will be necessary to clean the egr system with 68k and just install an occ.

 

you forgot to ask how old the 12 volt is

 

i was going to, but disabused myself of the notion.

 

I have experienced this a few days ago. It was a cold morning, and I drove short distance, about 10min. Normal operational as usual. Got back to the car after an hour and bah, the diesel noise was present and it lasted up to 10sec. I’ve never gotten this noise before, so it was definitely weird.