2010 Prius - P0401 after EGR & manifold cleaning

Hi guys,

Long post ahead - sorry in advance!!

I have only just created an account but have been lurking on this forum for a while. I recently bought a 2010 Prius with 250k kms (~150k miles) that was parked for almost 3 years outside for a very low price. I was extremely lucky with it, got it up and running just by changing the oil and hooking up a new 12v (it still had the original one, obviously toast after 3 years of sitting) HEV battery also looks good at 80% health according to Dr. Prius (most likely it was refurbished just before it was parked - the owner was a company that went bankrupt so the car was auctioned off) Car drives fine, no power issues, fuel consumption is around 4,5 liters / 100km (~52 mpg)

Anyway, it seemed to only have one code stored - P0401, the dreaded EGR insufficient flow code. I went ahead and took it to a mechanic that knows his stuff around hybrids and of course, the EGR, cooler, fuel injectors and intake manifold were full of junk :


But not a worry, the mechanic took care of it : (uploading pics just in case somebody wants to see a before and after)




Paid the man, drove the car home. No check engine lights; Car was performing very similar (didn't notice any performance issues even with the code) - maybe just a tiny bit smoother and less noisy.


200 kms later, the code pops up again! Very upset with that. Went on this forum and saw that the car does a certain test for the egr flow - mine was total crap. 0.17 kPa! Honestly looks like a full obstruction.


I read the huge thread that found the "ski jump" plastic bit inside the valve rotor to be the culprit. Went ahead and took it apart :





It looks fine to me! It certainly is not as smashed as in some pics I have seen on that thread. The valve itself also operates smoothly by hand.


I have also checked MAP values, 35 kPa at idle seems to be in line with what other guys were getting, so I'm assuming the MAP's fine as well...

So what else could it be? The only other suspect I have would be that the mechanic somehow messed up some gasket installation:



I'm refering to the gray - black gasket between the valve and the cooler itself. I'm thinking that shouldn't sit like that - maybe that's what's obstructing the flow! But then on watching some YT videos... it looks the same there.. And also, I don't see how you could screw that up, looks like it can only be installed in one position since it's held in by 2 bolts...

I've no idea what to do next. Can the stepper motor be bad ? As in, not functioning at all? I'm assuming that would've caused other problems.. like rough idle, rattling..


Thanks a lot guys and really appreciate all the knowledge sharing on here!

 

Hello guys! Yesterday was election day in Romania and waiting for the results kept us on our toes all night, so sorry for the late reply!
Thanks for your input! I'm going to try to reply to you all in this post:

@wukong sun that is an interesting point, but I don't really see any visual sort of issue with the valve's threads!

@Mendel Leisk Thanks for the very very detailed reply! I thought just having the actual 'slope' there, even with the rut in the middle was enough for the stop to do its job. Seems like the next step would be to either go hunt for another stepper motor at the junkyard (there was some guy on the forum who replaced it with a 1.3 Urban Cruiser stepper motor which looked identical), if not, time to buy myself a new OEM EGR!

As for what cleaning products were used, honestly, I have no idea; all I know is that the injectors were cleaned using ultrasounds. But I'll ask the mechanic anyway and report back if he provides an answer!

As for the whole operation's price, if you ask me, it was really darn cheap! Since you're interested I'll defalcate all the costs. Car got a thorough cleaning (EGR Valve, EGR Cooler, all the piping related to that; Injectors cleaned with ultrasound, Throttle body, intake manifold); I also replaced the gearbox oil (it was pitch black!!!!) - I provided the oil since I wanted to change it by myself but something got in the way so it was left for the mechanic to do - and lastly, brake fluid change.

Total costs (in US Dollars) : 330 $
EGR + assemblies(Cleaning bit) : 155$
Injector ultrasound clean : 45$
A/T oil change : 22$ (just labour charged - oil was about 45$ maybe?)
Brake fluid change : 78$

@ChapmanF , thanks for the technical explanation and the reinforcement of Mendel's opinion. Seems like I've got to hunt for a new valve / rotor!