Still P0401 after cleaning egr !! should we drive it?

There would have to be a lot more research/proof for anyone to manufacture this, but assuming uneven intake manifold port blockage is the real culprit, I wonder if it would be possible to replace the EGR pipe with some sort of particulate filter, which would be relatively easy to remove/clean.

 

Funny how I can find this post by searching google for "Prius EGR Ski Jump" word salad.

Sounds like the fix worked.

I'd like a little more explaination of the process involved?

You heated the inside bottom coil part (black plastic piece easy to remove) to make the plastic nice and soft, then molded it with a hot knife?

I'm pretty sure this is what's impacting my EGR, but I'll verify tonight when I pull off the coil.

Do you think it'd be possible to just install a small screw in place of the "ramp"? A very hard prominent stop, if you will.

 

I would not necessarily assume that what happened to ozmatt would be a common cause of other people's issues. Seemed like more of a coin-lands-on-edge story caused when ozmatt did a hot full-throttle hill climb on a 40 ℃ Australian day.

Well, I guess you've probably had some pretty hot days in Flagstaff recently.

It would be easy enough to take the stator off the valve, spin out the rotor, and post a photo of its ski jump.

I'm guessing most people's will be fine, but if yours has been mashed through, it will show in the photo.

The coils, by the way, are in the stator, the black cap you remove with the two screws.

The ski jump is on the inside of the rotor, the brownish plastic magnetic cylinder you see once the stator is off. You have to remove the rotor (spin it off the threads of the valve stem) to see the ski jump. Don't lose either spring.

 

In my case, the symptoms mirror OzMatt's - freshly cleaned EGR system still throwing codes. The EGR valve is fairly simple device, so if it failed I'd probably point to the ski-ramp and stop issue.

 

Indeed, it is such a simple device that looking at the ski jump will answer the question conclusively, more so than the pair of symptoms "freshly cleaned" and "still codes".

 

If it came down to EGR valve replacement, would there any advantage (or problem), getting the revised valve?

I believe the numbers are:

25620-37110 (older)
25620-37120 (newer)

 

I'm not sure anybody's even figured out what the difference between the valves is yet.

There does seem to be a bit of outside-dimensional difference.

 

We’ll my Ski Jump has been flattened a bit, but nothing substantial.

One thing I did notice however was the stem of the valve was very sticky. I’d push it in, and it would stick, so I tried to lube/grease the stem for easier operation. We’ll see how long I can go before the next CEL.

 

Huh. Unless that's just weird light, it does look a bit misshapen, doesn't it? Compared to an unmasticated one.



Maybe these things just aren't built for 21st-century Arizona.

 

When does the "stop" come into play?

What position is the EGR in at startup relative to the stop?

For example, could more pressure in the EGR system force the valve closed too quick, abusing the stop? Or vice versa?

 

It looks like the unharmed Ski Ramp has a more definite stop at the top. Mine was just a ramp with a flat top.

 

Lastly, what about replacing the plastic stop with a metal one? IE, a screw into the plastic?

 

The stop indexes the position when the valve is fully closed.

The actuator is a stepper motor. Depending on the sequence of pulses sent by the ECM, it moves one step at a time in either the closing direction or the opening direction.

Whenever the ECM doesn't want EGR, according to the repair manual waveform diagram, it is just constantly sending pulses in the closing direction. So the rotor goes to the stop and can't go any farther. Then later, when the ECM wants some EGR, it can send a certain number of pulses in the opening direction, and know the valve is that many steps open, assuming it was closed at the stop to begin with.

So when resting at the stop, there is always a bit of torque from the continuing pulses in the closing direction, trying to push it past the stop. Ordinarily, that's not going to do anything, unless the conditions are something like very hot driving on a very hot day, enough to soften the plastic enough for that pressure to deform it.

Then, if the rotor is able to go, say, five steps farther in the closing direction past where it was supposed to stop, then later if the ECM wants EGR at step 15 and it sends 15 opening pulses, the valve is really only open to step 10.

 

So why the ramp? Why not just a metal stop?

Which side do you suppose the metal nib comes from? When the valve closes, does the nib ride up the jump, or does it hit on the opposite side?

 

The idea of a metal reinforcement sounds kind of appealing, though I'm not sure how one would pull it off. I had thought of a flat piece of aluminum, heated and shoved into the plastic. I guess a tiny flat-head screw into the ski jump could work, as long as it doesn't protrude beyond the jump's original height.

Just not a lot of room there for doing that work.

Simplicity of construction, I'm sure. The rotor is molded out of plastic. If they thought a stop made of the same plastic in the same mold would be sufficient, that saves them further complicating the assembly and combining materials.

It hits on the flat cliff side; that's what makes it a positive stop. (When the plastic isn't mushy, anyway.)

 

Ok, so to recap:

EGR Closed - Resting on Stop
EGR Open - Away from Stop

Fault: Rotor goes past stop, ECM gets confused on how far it needs to open for sufficient flow.

Lets say the stop was too prominent or out of clock relative to what the ECM expects as full closed. The EGR would never fully close. Downsides?

 

Ahh then the ramp must be there for a reason.

I'd find it hard to believe that the ramp was formed when a scraper pulled the material up into the stop. The stop and the ramp appear molded intentionally. My belief is that the ramp is so the metal nib can slide up and over the ramp and stop during install.

Or the opposite - when we thread the rotor off, it goes up and over that ramp?

 

No. The ramp is formed in that shape, in that direction, in order to have a flat cliff surface that hits the metal nib and stops the rotation cold. Put the rotor back on the stem and observe the direction it rotates for the valve-closing direction. (That's the direction as you are threading it on to the stem, just like a nut onto an ordinary screw.) All of the 'ramp' material back of the cliff surface is just what reinforces the stop from behind.

Exactly. Notice that's the same direction as when the valve is being opened. In that case, the valve is all assembled, so the rotor, turning counterclockwise, does not thread off. Its bearings hold it in place, so instead it pushes the valve stem open.

Because there are multiple full turns of the rotor between closed and fully open, at the first full turn away from closed, the metal nib will still be pretty close to the ramp. But it will pass over without touching, and the shape of the ramp helps ensure that.

This thread has finally inspired me to crack open the old EGR valve that I removed from my car a year ago at around 155k miles.

Lo and behold, its ski jump is mashed.

So this may, indeed, be a more common failure mode than I had thought. Definitely something to check on any used EGR valve before installing, for sure.

 

Ah ok I got ya.

Interesting though that its only one full rotation. With all those threads, and the amount of movement in the stem, I'd think it winded in and out quite a bit.

Here's my thought:

A) Fairly small cap head self-drilling screw set into the plastic NEXT to the shelf. This would add 1-2mm of distance between original stop location and where it would end up with the screw. Using the original ramp as a guide for depth. If it didn't work, pull the screw, leaving ramp undamaged (or at least not more than it is). The cap head is nice because it provide a large surface area for which to catch the metal nib.

B) Fairly small cap head self-drilling screw into the top of the ramp - mirroring the original stop. Sunk into the plastic as to match the original height. I'm not entirely confident that a cap head screw would sink far enough into the plastic. Might require a small hole to be started so as to countersink the head.

C) Fairly small self-tapping screw that sits more flush with the top of the ramp.

I'm not sure how deep the plastic is here. If its only paper thin, a screw won't work unless I drill a pilot hole into the metal underneath.