EGR Valve, cooler, pipe...oops

These fellas have already narrowed it down to the science when it comes to EGR ciruit & manifold cleaning. Theres alot of reading catching up if you haven't been on board from the get go

 

From what I've read here the EGR system in the Prius is doing more more than just reducing emissions: it has a cooling effect on the engine, and disconnecting it will raise engine temperatures significantly. The best course seems to be restoring the EGR to as-new condition. Good for the environment too.

Maybe @mjoo can comment, I believe it's his assertion about engine temps raising.

 

Thanks for the reply, I'd be interested to hear more about it. Restoring the egr system is certainly the way to go for some diesel's as well, but they're so needy, that its worth it to delete them for reliability's sake. The egr on a diesel has no real affect on operation of the engine, outside of emissions.

I'm amazed by how much deep maintenance contemporary direct injection gas engines need.

 

Here's a graph I found doing a Google search: https://www.researchgate.net/profile/Arash_Nemati3/publication/261946687/figure/fig10/AS:296693493977104@1447748649563/Cylinder-pressure-and-temperature-variation-under-different-EGR-ratios-a-pressure-b.png

The research paper is here:(PDF) Decreasing the emissions of a partially premixed gasoline fueled compression ignition engine by means of injection characteristics and EGR

The Gen 3 uses 20% EGR. As the EGR system flow decreases, both the peak temperatures and pressures increase.

EGR is not only good for the environment - it's good for your wallet as well. It helps prevent engine damage from excessive pressures and temperatures and lowers fuel consumption. Toyota also has research papers that demonstrate EGR's merit in improving combustion and fuel efficiency.

The EGR system plugging is an unfortunate weakness of the Gen3 system. I hope they fixed it for good in the Gen 4 redesign.


Pixel XL ?

 

That's good information, thank you. It is too bad the system is so prone to fouling. I imagine a large percentage of these things are driving around with totally or partially plugged egrs. I know mine isn't running right, making noise, and only getting 33mpg. I'm willing to bet that is why the po wanted to get rid of it, and I haven't had time to take a look at either the egr or pcv but I expect they'll be in rough shape after 153k mi.

Does anyone know if the engine goes into limp mode (or different ign or fuel maps) if it senses low egr flow (or unplugged valve)?

 

Different engines will have different pressure and temperature curves. For example, compared to the engine mentioned by the research paper, Prius doesn't do compression ignition.

Pixel XL ?

 

Prius is not direct injection.

On the other hand, our son just got a Mazda CX-5, which is DI; his friend told him about Oil Catch Can and intake valve fouling, he was wanting to do it at first, but is reluctant now, after seeing the complexities of access. Also worried about warranty. Frustrating.

 

YW. I agree - there must be a majority of Gen3 with some level of EGR and PCV problems. If the computer program in the ECM threw a code and illuminated the check engine light because of low EGR flow - there'd be a TSB for complete and free EGR system replacement. IMO it can't detect insufficient flow because of missing sensor(s) required to measure EGR flow. So far there's a TSB for replacing the EGR valve when the stepper motor plunger gets glued by deposits - and nothing else EGR.

Hmm. Can you imagine the maintenance nightmares of cleaning an EGR MAF sensor! LOL they'd probably need cleaning every 5k miles!

Pixel XL ?

 

Code p0401 is for low EGR flow. It's mentioned in a letter we got from Toyota, titled WARRANTY ENHANCEMENT PROGRAM, noted as: May 2017, and SOSH-W11-1A. Not sure how, but the car apparently can detect low flow somehow. Part of the text:

Toyota has received some reports of a rough idle and/or tapping noise from the HV transaxle at cold start due to a sticking EGR valve due to excess carbon build-up. The engine warning light may also illuminate with the DTC P0401.

Regardless of that letter, I decided to inspect/clean the EGR circuit myself because: I didn't want to wait around for that code, coking up everything in the interim. It's also up in the air as to what they would replace: if it's just the valve and they leave the cooler, that's laughable.

 

Ok, that's right. It's T-SB-0027-16 mentioned in post #895 of this thread:
https://r.tapatalk.com/shareLink?url=https://priuschat.com/threads/new-service-bulletin-for-engine-knocking-at-startup-t-sb-0012-10.102200/#post-2604199&share_tid=102200&share_pid=2604199&share_fid=1171&share_type=t

What they do in that T-SB is replace the EGR valve and then reprogram the ECU. Why do they need to reprogram the ECU to fix a mechanical issue (EGR cooler plugging)? Is it to erase the fault detection? Or perhaps the T-SB just doesn't correct the fault if the cooler is plugged


Pixel XL ?

 

If they don't clean the cooler that's less than useless.

 

Wow that's disappointing - but I guess manageable for those willing and able to add egr cleaning to their maintenance schedule. I'm hoping that even with that, and the pcv sys, this car will be as reliable as I need it to be. And I can get rid of my wife's BMW that's been through two engines in 4 months.

 

What it would do is screw up the afr and the engine would try to compensate - that's probably why they run poorly when the egr's plugged. The only way around it would be to tune the egr out of the control software and I don't think that's something worth figuring out on these.

 

Our son's just got a 2018 Mazda CX-5, which has direct injection. He's on the fence about an oil catch can, concerned about voiding warranty. Any thoughts?

 

I'm not sure about that one, bud. If it were me I'd be extra salty if I had to resort to such measures on a brand new car. I'd get it through the warranty period and just keep an eye on things.

 

I cleaned out the extra EGR Cooler I bought. It was pretty clean and clear already.
I decided to try my pressure since I was cleaning the house and drive way.
It didn't do that good of a job. Not shiny at all. It did clear it out more than it was though.
So I guess using the pressure at least partially cleans/clears it.
So tomorrow I'll fill it with gunk and let it sit what I finish cleaning the house. Then pressure was it out again.

 

Install the occ, car breaks, remove occ and take to dealer for repair. After car is fixed, reinstall occ.

 

Same for passing visual state car inspection?

 

I'm probably going to have the car for about 3 weeks, when they go on vacation. Just sitting, looking at it... With this Moroso Air-Oil Separator at my side...