Question about carbon clogging in egr system

It's about an 8 bolt job or so all up on top of engine I believe 1/4 drive ratchet a few wrenches on a 75 degree day no issues I'm you're age too . On tech stream you can read the flow of egr in HG numbers I cannot rem how lowis getting bad 14 comes to mind Chapman I think recently posted the numbers good luck buddy .this exact problem blew my 2013 engine crack in no 2 piston crown . Now new engine

 

They won't clean it, they replace the parts. And it will be expensive.
If you can change the spark plugs, you are about half way there.
It's not really hard, just takes time. If you take your time and take one part at a time,
you can do it.
Use a pressure washer and oven cleaner on the egr cooler. And "Gunk" on the intake manifold
and other plastic parts. Don't use the oven cleaner on the egr valve though.

Maybe someone is near you from Prius Chat that would be willing to help you.

 

If we only knew where or which Mathis .

 

How bad is the gas mileage??? I was still in hi 40's at no 2 cyl fail . Like 46 47 similar to my gen2 .then no 2 code I knew what that stumble was is..

 

If you can get to the plugs you're halway there. See first link in my signature.

70's not that old, is it...?

 

Not really ...until you look into the mirror!

 

It's kind of a grueling job in a Gen 3 liftback. In a Prius c, the stuff is more exposed on the top of the engine, but in the liftback it's kind of buried off the inboard end of the engine and under the cowl.

The thread about monitoring the flow test results is this one. You can watch trends over time in the flow results and see what is happening way earlier than the point where a P0401 would be logged. That's very easy and comfortable to do, nothing but plugging in to the diagnostic port in the cabin.

The flow test results don't really cover the four individual passages in the intake manifold itself. Those are better just directly inspected now and then. But that job is easy.

 

"Mathis is a city in San Patricio County, Texas, United States. The population was 4,942 at the 2010 census."

 

"Mathis is an unincorporated community in Dallas County, in the U.S. state of Missouri."

 

From uniform clogging (the kind the self-test can detect), not much in the way of symptoms. The ECM has the flow test results and it controls how far the valve opens, so there might be nothing obvious, until one day it decides the clogging is too much and sets a P0401 code.

From nonuniform clogging among the four small intake manifold passages, you can get an engine that runs smoothly at low throttle and at full throttle, but gets a bit rough at mid loads where EGR is used. The EGR valve opens at those mid loads and then you have some cylinders getting too much EGR and some too little, resulting in roughness.

 

$800-$1000 at a dealer who will install a new egr cooler and valve. You will get no improvement in mpg unless it was totally clogged and giving you the code. An independent mechanic "might" do it for a couple hundred less if he has experience doing it on a Prius of this generation.

In most cases, reduced mpg is caused by an old high voltage battery. Or short drives of a few miles or less. Or high speed driving of 70 or higher.

If we knew where you lived you might get mechanic recommendations. If you still have start up rattles and brake booster codes I would not spend much time or money on the egr system. Repairs to the engine could include a refreshed egr if you shopped carefully.

 

165k is a symptom of clogging.

Someone reported blown head gasket symptoms with a v, today, with around 120k:

Violent shake and Misfire | PriusChat

 

Who knew?! Keep the EGR unclogged and the car never gets old!

 

Mendel has disclosed a previously secret rollback option for used cars. "Entrepreneurs" no longer have to pull instrument panels and send them to one of our helpful Priuschat members. No more unnecessary shipping delays. Now they clean the egr with oxiclean and a carwash and the miles dissolve away.

Since we have guys from Monterey:

 

Finding a fully cleaned cooler for a reasonable price might be a tall order. And cleaning the valve is quite easy. That's a lot of $'s to save a few hours labour. With your miles I'd just clean what you have, and would likely be best to replace the pliant gaskets on the intake manifold. That entails the interfaces with throttle body, cylinder head and egr pipe.

FWIW when I did ours around 70K kms, I replaced nothing.