Intake manifold cleaning and found this

Post a pic of the intake manifold?

 

Those are EGR passages. Look to be completely bunged up with carbon. See first link in my signature.

Is 391K miles or kilometers? You don't disclose your location.

 

Not sure. Any misfire codes, say P0301?

 

i think that dry junk is a result of the intake manifold port being clogged. the little hole on the IM is for the egr gas, which is basically oil mist air, which gets hopefully pushed back into the burning process. If that hole is clogged, then no more mist will come through. So the build up probably occurred in stages:

Stage1: the little hole was open, oil mist air was flowing and mixing with the intake air. gradually, oil deposits clung to the intake port metal and built up.
Stage2: over time, after a lot of build-up on the intake metal, the little hole became clogged complete, preventing any more mist coming through.
Stage3: normal intake air flowed through the big opening in the clogged port tube. this gradually sucked the "wet" oil out of the mass, and made it hard.

When i cleaned my IM, i very carefully scrapped that crud of the intake ports on the block, while running a shopvac, very close to the scraper. I also reached up in the block-side intake ports with a rag and some throttle body cleaner. the tip of the fuel injectors is in there and i tried to wipe them very good with throttle body cleaner, in case they were coated with gunk too.

 

"oil mist air" is more appropriate description of the PCV (positive crankcase ventilation) vapours? The EGR (exhaust gas recirculation) would more hot/dry gas, a little sooty.

 

yes, you are correct Mendel! Sorry for misleading the group here! I wasn't thinking clearly and got confused by the back and forth of which port on the block and manifold was clogged. So the little ports are indeed from the EGR gas; and the big port is a combination of the intake gas and pcv oil-mist gas. The PCV gas comes in at a lower port on the intake manifold.

After having said that, if the dry-debris engine port is the one with the clogged EGR port, which I think it is from the conversation, that would shed a different light on this problem, indicating the EGR gas, which should be dry and hot as you mention, seems to play a part in keeping the oily gunk on the engine side, oily and gooey, rather than dry it out. hmmmm!?!?

 

Cooled EGR gas might be warm and damp---with condensed water, preferably not oil. Water is an inevitable product of combustion of a hydrocarbon fuel. That's why cool tailpipes sometimes drip water.

 

A theory is there are a couple of things going on:
1. The Atkinson Cycle engine on the Prius keeps the intake valves open briefly during the compression stroke to lessen the compressed air. On a worn-in engine (burning oil) this can spit some oil into the intake manifold.
2. The EGR port closest to cylinder #1 clogs first due to it having a longer travel (furthest from EGR source). This plugs up #1 cylinder first causing a lean condition in cyl #1. A lean condition (without moist 20% EGR content) = hot and dry combustion which burns the oil regurgitated into the cylinder causing a "dry" carbon deposit.

That's impressive mileage for an engine without EGR maintenance. Especially one living on K-Seal. Seems like lots of highway mileage attributed to the long run. I bet @danlatu would love to see the innards of this thing.

 

'Lean' might not be the word you meant here. The key idea of EGR is that it's a mix of gases without much usable oxygen, so it can be added to the intake charge without changing how lean or rich the mixture is.

If you try to dilute the charge by letting more air in, that leans out the mixture. Or in the other direction, the mix goes too rich. But if you take a proper mixture of fuel and air and then let in some inert exhaust gas, you have still a proper mixture, just less of it, and a bit slower-burning.

 

Sounds like you've gotten good at it. How many hours do you have it down to?

 

Oven Cleaner is my idea... It works great! I believe RayTheEagle suggested the power washer,
which now I do also.
It sure makes it go by faster! I have a spare on I installed last Tuesday.
66,000 miles on the spare one, that is clogged. This is the 3rd time I've done it and the cooler
is completely clogged, can't see any light through it.

 

Egr clean did not solve the rattle or misfire. What could it be?