Techstream EGR Valve Blockage Data

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by jas8908, May 3, 2019.

  1. ChapmanF

    ChapmanF Senior Member

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    Maybe not such a bad idea to check misfires now and then just on general principles; lots of things besides EGR can cause misfires.
     
  2. wheezyglider

    wheezyglider Active Member

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    Sure. But since this thread was about using data to detect "EGR valve blockage", here's another way.
     
  3. ChapmanF

    ChapmanF Senior Member

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    We already have a monitor test that is specific for what this thread is about.

    Checking for misfires is a good idea, but isn't specific to what this thread is about, because misfires have many causes.

    Absolutely, if you detect misfires, you might well check the EGR flow monitor value (and physically inspect the manifold ports) to find out whether your misfires might be related to EGR (and if you find out they aren't, go on and work through the rest of the possible causes).
     
  4. wheezyglider

    wheezyglider Active Member

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    You're a hard guy to collaborate with :)
     
  5. Norryboy1a

    Norryboy1a Junior Member

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    Since my noticing how badly my egr cooler was blocked, (95%) I'm beginning to think that there could be an additional blockage within the coolant heat recovery system. After all, isn't that also a place of restricted exhaust flow? Do you think that it maybe causing problems upstream?
     
  6. ChapmanF

    ChapmanF Senior Member

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    The EHRS is a bit of a different story, because EGR actually wants the exhaust gas back in the cylinders to play some role in combustion; EHRS just wants to get some of the heat back.

    Clogging of the EGR cooler therefore results in a reduction of gas returned to the intake. Clogging of the EHRS exchanger could only show up as an increase in exhaust backpressure. That could be a thing, but I think kind of a limited thing. The repair manual excerpt that Mendel posted here explains how the EHRS works.

    ehrs.png

    Only while warming up is the exhaust forced to flow through the exchanger portion. Once the coolant is up to temperature, the thermostat rod opens the exhaust flow control valve and the exhaust flows straight through, so it can't matter how clogged the exchanger is at that point. Also, per the manual, the valve "can also be opened by exhaust gas pressure to prevent insufficient acceleration performance when the engine is cold."

    That's why I expect that any increased backpressure from the EHRS could only be a thing during warmup and a limited thing even then.

    It's possible that an older EHRS just gets worse at recovering exhaust heat. Shortly after first realizing there are two coolant temperature sensors, one in the cylinder head and one right in the hose returning from the EHRS, I tried a cold start of my engine and watched both temperatures in Techstream as it warmed up. They were within a few degrees of each other the whole time. But I've got about 150,000 miles. It would be interesting to see what that looks like in a new car; maybe the EHRS return would be considerably warmer in the early stages then.
     
  7. Norryboy1a

    Norryboy1a Junior Member

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    Could be. Thanks
     
  8. burebista

    burebista Member

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    Best value to date.
    woot.jpg
    Nothing special happened, same trip to my brother in law.

    Also a couple of weeks ago I did a 500 miles trip and I measured that value on the road from time to time. It was all over the place, from high 14's to low 18's.
    If EGR cooler/valve is clogged I'd expect roughly same values but it seems like something else is influencing this value not only clogging.
     
  9. ChapmanF

    ChapmanF Senior Member

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    Yes, take a look back at post #111. The ECM is stuck with running the test under widely different conditions, because it is a test that the ECM sneaks in while you are driving the car.

    The other interesting note from #111 is that the "min" value reported for passing is not a fixed value. Some of the tests reported with the lower measured values also had lower "min" limits shown. It seems the ECM grades this test on a curve, possibly because it knows about the difference in conditions when it runs the test.

    That suggests it might be nice to know whether the quotient (test value ÷ min value) would be something that jumps around less than the test value by itself.

    For example, in two test results discussed in that post, one had a test value of 17.69 and the other had a test value of 12.75, a huge range.

    But when scaled by the "min" values that were reported each time, it comes out (17.69 ÷ 0.91) = about 19, and (12.75 ÷ 0.56) = about 23. Seems less bonkers that way.

    Did you happen to write down what the "min" values were for these recent tests you looked at?
     
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  10. burebista

    burebista Member

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    Nope. :(
    Next time I'll note those min values.

    Thanks for explanation, great as always.
     
  11. gromittoo

    gromittoo Active Member

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    It has been about 3 months and 8k Miles since I performed my major surgery cleaning the EGR system in my 2013 Prius V. I did a spot check recently on the EGR FLOW INSUFFICIENCY, while I had TS up and running changing some TPMS ids. I am concerned because three tests in a row were in the 11.8-13.5 range. I was in a hurry to get to work driving, so I did not take screenshots.

    Back in Late June / early July, I did three banks of tests:
    - Prior to doing any cleaning:

    - EGR-2013PRIUSV-094.290.miles-PreClean: 14.76 kPa
    - EGR-2013PRIUSV-094.362.miles-PreClean: 15.09 kPa
    - EGR-2013PRIUSV-094.432.miles-PreClean: 14.90 kPa
    - EGR-2013PRIUSV-094.507.miles-PreClean: 15.60 kPa
    - EGR-2013PRIUSV-094.569.miles-PreClean: 15.41 kPa​

    Average: 15.16 kPa; 1 Standard Deviation is .35 (+/- 2%)
    -Post EGR Cooler + EGR pipe
    - EGR-2013PRIUSV-094.753.miles-HalfClean: 20.56 kPa
    - EGR-2013PRIUSV-094.809.miles-HalfClean: 15.68 kPa
    - EGR-2013PRIUSV-094.893.miles-HalfClean: 15.60 kPa
    - EGR-2013PRIUSV-095.003.miles-HalfClean: 15.66 kPa
    - EGR-2013PRIUSV-095.105.miles-HalfClean: 15.54 kPa

    Average: 15.64 kPa*; 1 Standard Deviation is 0.035 (+/- 0.2%)
    -Post Cleaning the IM, I got a bad stumbling, plus the following errors (but they went away quickly)

    PostIntakeManifoldCleanCodes-2021-07-15 175220.jpg

    I cannot seem to locate the 5 screenshots I believe I took in July after the complete job. Now that it is October, I am concerned that the EGR values have fallen below pre-cleaning values. The single 20.56 kPa value suggests to me that something went suddenly wrong, and my more recent measurements indicate I need to take action.

    My gut tells me that something caused the EGR valve to stick after the 94,290 mile point. That would make sense, because I could not get the Phillips screws off the EGR to get it completely apart. I used Purple Power, water flush, followed by mechanical scraping of the parts I could get to. I finally did use some carb cleaner.

    I will add to this post, once I get five reliable data points. I needed to unhook the battery on Friday to work on the steering wheel, And we were away for the weekend with the 2017. I don't have any data for today.

    Two other side notes:
    1) I checked the 2017 Prius V a month ago (42k miles), and its EGR FLOW INSUFFICIENCY was near 19.5. It's first oil change is coming soon, and is my intention, I will check the EGR FLOW INSUFFICIENCY at every 5k / six month oil change.

    2) All of the 10 screenshots I took have a minimum value of 0.99. I am hope that indicates a good thing like no leaks in the IM or EGR system.

    I will post data from 5 test points.


     
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  12. burebista

    burebista Member

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    OK, since my last post I take a look every morning at that value.
    One day was 15 kPa with min. 0.91 and all other readings were 18.xx kPa mostly and a couple of 19.xx kPa with minimum 0.91 or 0.95 ( don't know how/why that minimum value changes because one day I've had 18.xx with 0.91 and next day 18.xx with 0.95).

    Hope it helps someone. :)
     
  13. ChapmanF

    ChapmanF Senior Member

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    Hmm. The "throttle/pedal position sensor" fortune cookies are badly worded, methinks. A Prius has sensors in both places (at the throttle body actuator and at the go pedal), but those codes are all about the sensor at the throttle body.

    With that emendation, that whole list of codes looks like a pretty good checklist of the exact things I probably would have unplugged in the course of doing an IM cleaning job.
     
  14. gromittoo

    gromittoo Active Member

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    I included the mention of the stumble and screenshot for completeness. The stumble and codes went away by themselves, and in the 7000+ miles I have driven since then (almost 3 months), they have not come back by themselves. I have seen no codes, or unusual behavior. My mileage is consistent with the use of the air conditioning.

    I ran over a six pack of bottled beer that fell off of someone's car a few weeks ago. It was a slow leak requiring a top off once a week. Then last week, a total flat. If not for the flat tire last week, I would not have taken the time to pull out my laptop to change the TPMS Id for my right rear tire to match one of the two full size spares I have. And I would not have thought to check the EGR FLOW. The 2013 Prius V has been driven a total of 4 miles since I disconnected the battery last Thursday for an unrelated reason, so I will get 5 new values, about 150 miles apart over when I restart Ubering this week.

    I am worried that I might have to do a "Do Over" of the cleaning, and possibly replace the EGR if I damaged it. It won't take as much time as I will have done it before, and the temperature will be more reasonable. Oh, and I won't take so many pictures.
     
  15. burebista

    burebista Member

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    Lately I saw values in high 18's and low 19's. Looks good so far.
    Today on my way to my brother in law I fired up Torque and tried to see how EGR valve position correlated with MAF and MAP sensors. It looks like they correlate somehow.
    EGR closed, low values for MAP and MAF.
    Screenshot_20211009_094526_org.prowl.torque.jpg

    EGR open, high values for MAP and MAF.
    Screenshot_20211009_094443_org.prowl.torque.jpg

    And a graph with EGR open.
    Screenshot_20211009_094236_org.prowl.torque.jpg

    So it looks like EGR valve and cooler works but I don't know how clogged they are because I don't know what values should be for MAP and MAF sensor with a clean EGR valve/cooler.

    Anyway, maybe it's useful to take a look at those sensors to see if EGR valve/cooler are working.

    Hope it make sense. Or not. :confused:
     
  16. gromittoo

    gromittoo Active Member

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    I measured my 2017 Prius v with 43.5k on it recently. It was at 19.5. kPa seems to be a really good value.

    On my 2013 Prius v, the first reading after cleaning the EGR cooler was 20.5, which quickly dropped to 15.6. Lately it has been much lower (in the 12's).

    My 2013 became a brick on Thursday night. I was driving a passenger with all the windows down. I heard a bang under the rear of the car that sounded and smelled exactly a medium sized firecracker. One block later, I lost power steering, and I coasted into a parking space in front of my passenger's house. The car would no longer go into "ready mode" and a whole bunch of lights. Torque Pro said B1000. The car was towed to the dealer, who will look at it first thing Monday morning.

    Here is the link to that saga:
    https://priuschat.com/threads/my-2013-uber-vehicle-died-after-making-a-loud-noise.228622

    All this is to say my promise to post new values is on hold for now.
     
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  17. ChapmanF

    ChapmanF Senior Member

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    Comparing the EGR valve position to the MAP sensor reading is exactly what the ECM's built-in EGR monitor test does. When you pull up the test result, you are seeing the amount of change in the MAP reading when the EGR valve was opened a certain amount.

    Complicating the interpretation is that the tests are done during live driving conditions, and the MAP and MAF readings are very dependent on everything else that is going on. The built-in monitor probably has better heuristics for sorting out what part of the effect is EGR than we have. Among interesting things I've noticed it doing, it doesn't always report the same "MIN" value to pass the test ... it grades on a curve, probably based on the conditions in play when it ran the test.
     
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  18. burebista

    burebista Member

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    A question. Probably doesn't belong here but I'm curious. :)
    Right above that EGR monitor sensor is another one: Catalyst Monitor Bank1 and it's very close to minimum value. Always.

    cat_sensor.jpg

    No lights on dashboard, no codes, but I'm curious what it means. Catalyst near end of life? Or something else?

    Thanks.
     
  19. Mendel Leisk

    Mendel Leisk Sand Pounder

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    Depends on which end of the scale is "bad"?
     
  20. ChapmanF

    ChapmanF Senior Member

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    The low end is the end-of-life end. Mine is pretty close there too. (It would make some sense to pull the number again some months or a year apart and look at how fast it is dropping, which might not be very fast. I haven't done that yet.) I am using it as advance notice to put some pennies in a jar.

    The test measures the oxygen storage capacity of the catalytic converter, which declines over time.
     
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