Lost 10mpg after EGR clean, etc. Now losing mind!

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by FriedCells, Oct 12, 2020.

  1. FriedCells

    FriedCells Junior Member

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    First, I've read every single thread for days now on mpg loss and other similar situations but I'm just more confused than before, and thinking that I need more stuff repaired than I probably do. So, I have a 2011 Prius. It has 156,000 miles on it. I recently did a lot of work on it. Before the work, I always averaged between 48-49mpg's consistently over the years regardless of the season (Live in San Diego). Occasionally reached 50+ on a tank. And occasionally 47. But never lower. Very consistent. After the work, there was an immediate drop of 10mpg's! I get now between 38-41mpg's. And I have to do all kinds of hypermiling techniques to get 41. And I have no lights, codes, etc. It's driving me crazy. It's been probably 6-7,000 miles since the work. And I can't figure it out. Work that I did:
    • @ 132,000 miles - Changed spark plugs and new Optima Yellow top 12V battery
    • @ 149,000 miles - Drained and filled transmission fluid, and both coolant reservoirs
    • @ 150,000 miles - Installed new PCV valve, added oil catch can, cleaned intake manifold, throttle body, MAF and MAP sensor with MAF sensor spray, new gaskets on all those, cleaned EGR cooler/valve to near new condition, rebuilt and bled brakes, changed all interior and exterior lights to LED's
    The drop in mpg's came after the 150,000 mile work. I first thought it was the computer relearning the new parameters. I even had one tank that my mpg's were really good. But then it returned back to near 40. The car feels like it's running better than ever. Stronger, smoother, etc. I had a P0101 code some days after the 150,000 mile work. I figured it was normal after such a change in everything, deleted code about 6,000 miles ago and it never returned. We had unusual heat lately, I thought maybe was because of too much AC. But the last couple of weeks, the temperature has been in the 70's/80's. Mild. Tried with no AC or low AC. Still 40mpg. I've touched my rotors after long drives to check for heat/brake drag. They are not even slightly warm. Cool to the touch. I even bought a new MAF sensor thinking maybe the cleaner damaged it. No change. I went over the OCC install twice and added permanent thread lock to any connectors to seal any potential vacuum leaks. No change. I removed and double checked the throttle body, intake, gaskets, made sure all connectors, all seals, all hoses are in place, clamped good, screwed tight. Still consistent 38-40mpg's. Please give me ideas what to check next. I severely miss my 49mpg's and am losing my mind and time with how many times I've checked things again and again.

    Things I've considered:
    • Maybe traction battery. (But the mpg's immediately dropped after the work. Overnight from 49 to 40. Seems like traction battery would lose mpg's more gradually if it was going bad)
    • Maybe spark plug coils? They looked good when I changed the plugs. Didn't change them. But there are no signs of misfire or hesitation. Runs very strong.
    • Fuel injectors? I doubt this because I have used Lucas upper cylinder lubricant/fuel injector cleaner every 5,000 miles or so for a long time and also use only top tier detergent gasoline from Costco or Arco.
    • Fuel pump? Also hard to believe as the mpg's dropped instantly after the work. Not gradual, but instantly overnight after the work.
    • Thermostat? See edited info below.
    So, it seems connected to whatever work I did. But what, and how do I figure it out? I have Techstream software, but haven't used it much except to change backup beeping and other little things. I also have a Carista OBD dongle and Torque, Carista, Dr Prius apps. Anything in all of this that I can use to narrow down the problem?

    Edited and added info:
    I'll add a little more backstory that I just thought of in case it's useful. At around 145,000 miles, I had my car overheat going up a long incline at maybe 80 degrees outside. I had driven that incline before and other much longer mountain drives without overheating. It was that event that got me to do all the 150,000 mile work, thinking that draining/changing coolants, cleaning the EGR, etc would help. While I was at it, I figured I'd do all the other stuff that I mentioned. About 3 weeks ago, even after all the work, I had another day that my overheating coolant light came on. But this day was the hottest day of the year here. I was inland and it was 117 degrees out. I had AC on full blast, and was climbing a sustained, steep 2 mile incline. I just figured under the extreme heat, and long incline, that maybe it was to be expected. It hasn't happened since but temps have been much milder here in the last weeks. I've seen some arguments on PriusChat that the engine should never overheat even in these conditions, and others say that it might be normal. Would a bad thermostat throw any codes? I've use torque app to monitor temps while driving and it seems normal and steady in the 180-190 degree range. But then I'm not super sure on what else to look for regarding the thermostat.
     
    #1 FriedCells, Oct 12, 2020
    Last edited: Oct 12, 2020
  2. ASRDogman

    ASRDogman Senior Member

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    Did you clean the EGR Cooler? Or just he EGR Valve?
    Go over everything, slowly, double check you didn't leave something disconnected.
    Usually you'll get a code.
    Did you replace front and rear pads? Rotors? The rear brakes pads have the pins that need
    to be aligned with the puck. A lot of people do this incorrectly. Check the rears carefully and see
    if they are wearing at an angle. Even though the rims are not hot, they may be wearing enough to
    effect fuel mileage.

    Since you have Techstream, use it. The main reason I got it was to disable the stupid back up beeping....
    ONCE is more than enough for me. :)
     
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  3. fotomoto

    fotomoto Senior Member

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    Low hanging fruit: tire pressures, change in fuel supply/quality.
     
  4. FriedCells

    FriedCells Junior Member

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    Yeah, I went over everything more than a few times. I misspoke when I said I did the EGR valve. I meant that, yes, I removed the entire cooler, soaked in Oxy-clean, pressure washed it to being in new condition, etc. I replaced front and rear brake pads and rotors at the same time, rebuilt calipers with new boots, gaskets, and lubricated the caliper pins, and yes, saw Mendel's pics on how to properly align the puck, have checked the pads after. No issues there at all. And I wish the car would throw a code so I'd know what to do. But no codes. Any idea specifically on what to do in Techstream to narrow it down?
     
    #4 FriedCells, Oct 12, 2020
    Last edited: Oct 12, 2020
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  5. FriedCells

    FriedCells Junior Member

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    Always kept my tires at the same PSI. Check them every week and have a digital inflator that keeps them exactly where I like them. Always used same top tier gasoline. No change there.
     
  6. JC91006

    JC91006 Senior Member

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    I would check your spark plugs, make sure they are gapped correctly. You did use the correct Denso or NGK plug correct? What type of oil are you using? 0w-20?

    As the car ages, you will lose engine efficiency and the HV battery will not provide as much power. But since you noticed the changes after your service, then it probably is not all engine and battery related.

    Have you performed a reset of the 12v battery? After you clean the MAF sensor or throttle body, you usually have to reset the 12v battery.
     
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  7. FriedCells

    FriedCells Junior Member

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    Yes, used NGK, bought at O'Reilly's, confirmed for my vehicle. Checking the gap on the plugs is a good idea. Only thing is that the drop was instant after the 150,000 mile work. Was fine before that and plugs were installed at 132,000. So unless the gap coincidentally changed overnight after the 150,000 mile work, I would doubt that's it. But it's worth a check, albeit timely with the removal of the wiper cowl.
    Using 5w30 Mobil 1 synthetic. But I've been using that since about 125,000 miles. Was on 0w20 before that. Didn't seem to affect my mpg's much after the change. Was actually recommended by Toyota dealer mechanic to slow timing chain cover leak.
    And yeah, I do expect to lose some HV/engine efficiency over time. But the instant drop leads me to believe that I must be getting too rich a fuel mixture after my work. Just can't understand why there's no code for something if that's the case.
    And yes, reset the 12V battery. Even was reset again about 1,000 miles ago as I disconnected it for some other work.
     
    #7 FriedCells, Oct 12, 2020
    Last edited: Oct 12, 2020
  8. JC91006

    JC91006 Senior Member

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    Maybe your parking brake is rubbing. How did you rebuild your brakes? Why did you rebuild them?
     
  9. FriedCells

    FriedCells Junior Member

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    I rebuilt them only for peace of mind. I figured if the original brakes lasted 150,000 miles, then doing that work would give me peace of mind for another 150,000 miles. I rebuilt by taking off and replacing pads and rotors, new shims, new grease on shims, new brake holding springs, and guides, removed calipers, bought rebuild kits for calipers with all rubber boots, gaskets, square seals replaced, permatex ceramic highest quality lube grease on all components, pins, pistons, etc. Forgot to mention that I also bled the brakes, and new fluid run through. I also adjusted the parking brake after the work. The rotors are cool as a cucumber after long drives. Definitely 0 brake drag.
     
  10. jzchen

    jzchen Senior Member

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    My suspect is the PCV valve. If you still have the old one swap it back and see.

    moto g(7) power ?
     
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  11. FriedCells

    FriedCells Junior Member

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    I appreciate the response. I do not have the old one anymore. But I did buy the new one directly from my local Toyota dealer. I gave it a good shake before installing it and heard the clear opening and shutting of the valve as intended.
     
  12. FriedCells

    FriedCells Junior Member

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    I'll add a little more backstory that I just thought of in case it's useful. At around 145,000 miles, I had my car overheat going up a long incline at maybe 80 degrees outside. I had driven that incline before and other much longer mountain drives without overheating. It was that event that got me to do all the 150,000 mile work, thinking that draining/changing coolants, cleaning the EGR, etc would help. While I was at it, I figured I'd do all the other stuff that I mentioned. About 3 weeks ago, even after all the work, I had another day that my overheating coolant light came on. But this day was the hottest day of the year here. I was inland and it was 117 degrees. I had AC on full blast, and was climbing a sustained, steep 2 mile incline. I just figured under the extreme heat, and long incline, that maybe it was to be expected. It hasn't happened since but temps have been much milder here in the last weeks. I've seen some arguments on PriusChat that the engine should never overheat even in these conditions, and others say that it might be normal. Would a bad thermostat throw any codes? I've use torque app to monitor temps while driving and it seems normal and steady in the 180-190 degree range. But then I'm not super sure on what else to look for regarding the thermostat.
     
  13. Mendel Leisk

    Mendel Leisk Senior Member

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    Maybe verify rear pistons have maintained proper orientation: raise rear and check free-spin of wheels. There will be slight drag, but wheel should spin 2~3 revolutions with a good push.
     
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  14. FriedCells

    FriedCells Junior Member

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    Thanks for the response. I have done that but I guess I could do it again. I saw a video on Youtube of a guy showing the proper amount of rotations with good brakes on a Prius. And while watching the video, I spun mine at the same time that he spun his, and it spun the same rotations. About 2.5-3 rotations. But doesn't hurt to check again.....
     
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  15. Mendel Leisk

    Mendel Leisk Senior Member

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    It sounds like you've got it covered. (y)
     
  16. FriedCells

    FriedCells Junior Member

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    I've tried almost everything that I can think of or find online. Only thing that I haven't done is take the OCC out of the loop. But it's extremely well sealed and I'd assume a code if there was an issue there. Besides that, I'm lost for what to try next. Things I will do next are check rotation of rear wheels as you suggest, check gap of spark plugs as another guy suggested, test HV battery with Dr Prius app, check movement of EGR valve to ensure it's not sticking, and if nothing gets my mpg's back, I'm really lost. Next thought is maybe bad thermostat....
     
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  17. jzchen

    jzchen Senior Member

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    You overheated but I didn't see mention of replacing the oil?

    moto g(7) power ?
     
  18. FriedCells

    FriedCells Junior Member

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    I didn't mention it, buy yes, oil was changed after both overheating occurrences. And i check my oil regularly also. I am never low on oil. Despite my miles, my car burns very little oil.
     
  19. royrose

    royrose Senior Member

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    You mentioned the Dr. Prius App. Have you run the hybrid battery health checks? If so, resistance and charge levels about equal?

    Have you checked that the inverter coolant pump is working by looking for swirling in the coolant when the vehicle is in ready mode? Some people change the inverter coolant pump as preventive maintenance around your mileage. I actually doubt this is an issue because you have no codes but it might be worth checking.
     
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  20. ASRDogman

    ASRDogman Senior Member

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    I have only used techstream a few times. I've been fortunate to NOT have to use it.
    But one way to learn is to hook it up and start checking things out. That's how I figured out
    how to turn off that stupid back up beep.

    I've tried searching for ANY type of instructions on how to use it, but haven't found anything
    worth the effort of the video they made.

    But you can test the engine coolant pump, and inverter pump with it. If the coolant pump is getting weak,
    they it's possible under heavy load the engine could run hotter than normal.

    And NO, it should NOT over heat. If you had overloaded the car with people and/or "stuff", then it's possible.
    Or if the plugs are the cheap china copies, they could be falling apart and not giving a good spark under
    the heavier load of going uphill.

    There are some fake NGK plugs out there. Same as Denso plugs. Some of reported getting them
    from Toyota. So checking them is a good idea. You'll certainly be able see if they are the real thing
    or the fakes. If they are the Iridium plugs, like they should be, you should NOT have to adjust the gap.
    I am not certain about the NGK plugs, but I think that holds true for most if not all Iridium plugs
     
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