2010 Revving and Misfiring

I would clean the cooler and go from there

 

How’s the engine coolant level?

If lower than you remember, you might be in head gasket land.

Good luck and keep us posted .

 

If you clean the cooler, swap the spark plugs since you’ll be taking the windshield wiper cowling off.

You’ll be there anyway and near the mileage to do so.

Good luck and keep us posted .

 

On the many Prii I have worked on (over 12 gen3’s), the valve has always been closed.

That’s it’s default position when not magnetized, unless there’s something prohibiting that.

I’d say a thorough cleaning is in order.

 

The valve is spring loaded closed. The black cap can be removed, the magnet removed and the inside chamber can be cleaned. I would not let liquid into the pintle shaft or on the lower magnet bearing, but you could brake clean or OxiClean soak it to just below the top of that inside chamber. Hopefully that helps to unbind it assuming the springs haven’t failed under the magnet. I used some brass brushes on a drill to remove the gunk and clean the gasket interface areas.


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Keep this side clean and free of water or cleaner. There is some type of grease on the thread of the magnet, not sure what kind.

That spring is what keeps the valve closed.






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The EGR valve actuator is a stepper motor, with the valve's full range of motion being (IIRC) 111 steps, as the magnetic rotor spins on the threaded pintle shaft.

There has been a little mystery on PC about whether the ECU knows what step the valve is on if it has been disassembled that way. I would assume it can just attempt to step in the 'close' direction more than 111 times and then say "ok, wherever I was, now I know where I am", and the spring construction also suggests that. But oddly enough, there was a recent thread (I doubt I'll be able to find it) where someone had disassembled and reassembled the valve, and afterward it seemed to be acting as if the positioning was off.

Were there any EGR-related codes? The ECU does conduct self-tests now and then.

 

I would suggest to clean the valve without doing any disassemble, ie: taking the black cap off. It's more difficult, but maybe safer, all things considered.

I cleaned the best I could from both ends, and then gently pried up the flange, cleaned the contact zone.

If it was was stuck open, would there be a warning light and code (besides the misfire code)?

How's the cooler looking?

 

That carbon coking will foul the movement of the valve pintle between the inner chamber and where it exits the top. I’m not sure what is in here but there should be something that prevents flow of exhaust gas through the pintle shaft but still allows the shaft to move. Some have thought about applying a grease here which might just attract more crud. I used a little brake clean in there and it loosened everything to allow free movement. Lots of history of these binding open or closed.

During reassembly, the magnet will try to unspin it self. What I did to ensure it’s all closed properly is to spin on the the black cap thus tightening down the magnet. I also used a micro screwdriver in one of the 2 little slots just under one side of the black cap to hold the magnet in the fully down position and prevent it from spinning while I secured the black cap.





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So my valve stays closed so no problem keeping cleaning solutions inside. I put a mild Oxi solution with hot water in there and let it sit for say 2 hours. Did the rest with brake clean and brass brushes. No issues.

Edit: I should note that I for this one I actually unthreaded that spring so the valve naturally falls open and then used a c-clamp to hold a hockey puck over the valve opening so I could get both sides of the valve in the same soak. Maybe a little overkill, but it’s sparkling clean.

I’ve read the concerns here with oxi-Clean vs aluminum which is why I chose to limit my soak time and go easy on the oxi. My goal was just to soak it enough to loosen the gunk and use brushes and brake clean to finish the job.

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Oxi is good on the cooler. On the valve should be cleanable with carb or brake cleaner. The cooler is stainless steel, but the valve is mostly aluminum and likely to tarnish. Might just be cosmetic, but I would avoid oxi for the valve.

 

Techstream does have a test that allows you to take control of EGR and manually set the step. This is done through Engine and ECT - Active Test.

The FSM states:
A/C and all accessory switches off.
Engine in Inspection Mode and coolant 75C or more.
Shift lever in P or N.
Do not leave EGR valve open for 10 seconds or greater.
Return step to 0 when Active test complete.
Do not open 30 steps or more during Active Test.



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