Prius won’t get over 30mpg after new engine installed

Discussion in 'Prius v Technical Discussion' started by Chardone69, Apr 29, 2021.

  1. Chardone69

    Chardone69 New Member

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    I have a 2012 Prius v that blew the head. I still drove it for approx 10k miles after it popped and was getting 33-35mpg with the blown/cracked head. So I installed a remanufactured motor with all new plugs,coils,fuel injectors,VVT solenoid,cam and crank sensors,Egr cooler and a new upstream O2 sensor. Now this car won’t get over 30.2 mpg and it struggles climbing hill now. Could this be a bad ECM? A bad TCM? Bad mass airflow sensor?Transmission or Damper? Or could it be in the hybrid system? I can’t figure this out and have been scratching my head for four months now.
     
  2. Chardone69

    Chardone69 New Member

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  3. Tim Jones

    Tim Jones Active Member

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    Do you have any codes?
     
    #3 Tim Jones, Apr 29, 2021
    Last edited: Apr 29, 2021
  4. Chardone69

    Chardone69 New Member

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    No codes. It was eating coil packs on the number four cylinder until I got one from the dealership. Now it seems to run fine. Just really crappy mpg
     
  5. bisco

    bisco cookie crumbler

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    is the inverter pump working?
     
  6. Tim Jones

    Tim Jones Active Member

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    bisco and privilege like this.
  7. Samuel Williams Jr

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    Your gonna need a scan tool or you'll just be guessing. And a compression test of the engine would be a good idea also.
     
  8. Tim Jones

    Tim Jones Active Member

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    You would think there would be a CEL
     
  9. Chardone69

    Chardone69 New Member

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    Engine is practically new and it has perfect compression in all cylinders

    I hope your trying to be funny because it’s not the light as it was on the car before the engine swap.

    No codes. It was eating coil packs on the number four cylinder until I got one from the dealership. Now it seems to run fine. Just really crappy mpg

    How do I check whether it’s working or not?
     
    #9 Chardone69, Apr 29, 2021
    Last edited by a moderator: Apr 29, 2021
  10. Samuel Williams Jr

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    Well you'd think? But even if it did, it still would not tell you what was wrong? The Prius can be a Drama Queen, with it's Dash Board, lights. It can have an issue store a code and continue to function. It will work around the issue (if it can) and continue to function, while not bothering you with it until it can't?

    And when it can no longer work around the issue. Our Gen Two threw a fit, lit up everything on the Dash. At 45 mph the motor quit, ie the gas pedal did nothing?? But around 34 mph it kept going in silence, on Battery. The battery was going flat so I looked for a place to pull over and call for a tow truck back home.

    At first when I shut down it would not start. But while waiting for the Tow Truck, it did start?? And the Hi Voltage battery went back to full. So screw the tow, it was 6 miles to home so, I'll try and make it? 60 mph without issue, for 5 miles but the Red Triangle was still there?

    Now this is where it tick's me off. I tried to scan it but none of my scanner's read Toyota? So off to the dealer it goes the next day under it's own power. And we get a call from Toyota that it is the Down Stream O2 sensor.

    I know it was the second one because we have the record's for the car and the up stream O2 and the Cat, had been replaced under warranty before we got the car. The part that "still," ticks me off is "two week's" of no car and $450 buck's for an 02 sensor??

    I add Wide Band O2's to older upgraded turbo car's, that don't have them, no big deal. But without the right Diagnostic Tools, with today's car, you have no idea what is going on under the hood?

    You really can't play "Whack A Mole," with today's car's. That get's expensive. But you could at least have it scanned and see what show's up???
     
  11. Tim Jones

    Tim Jones Active Member

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    I have Toyota Techstream and adapter..... pretty sure it was under $50 on ebay or amazon.....
     
  12. ChapmanF

    ChapmanF Senior Member

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    O₂ sensor readings and codes are in the ECM and should be available to a standard OBD-II reader. There must be more to the story why those wouldn't have shown up in that case.

    For the OP ... it would be handy to have Techstream, and to do some logging of engine data on your test drive, including the difficult hill ... especially if you'd be able to get access to a working Prius v and take it around the same course logging the same things ... rpm, MAF, fuel injection, ignition advance, cam advance, etc.

    Here's an example from another recent thread.

    [​IMG]
     
  13. Samuel Williams Jr

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    Cool and from what I know that would be the one.

    But maybe start a new thread to ask about using it? I know nothing except maybe needing an older Windows Laptop??
     
  14. Samuel Williams Jr

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    You very well my be correct? It was two year's ago and we just got the car. I lifted
    the hood to see the "motor," and freaked out. Screw this the I saw inventor and orange wires? Fuel and oil that I understand. I closed the hood and walked away.

    But without being under stress, I'll try the scan tool I already have and see what it show's if I can find it. :)
     
  15. Chardone69

    Chardone69 New Member

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    I put the car in READY mode and don’t notice any movement in the inverter tank and I don’t hear the pump running. The only movement in the tank is from my fat butt leaning over the fender to look inside the tank. Start the motor and still no flow. I’m thinking that’s the problem as the engine itself seems to always want to run unless I’m doing under 40mph or start from a dead stop. The hybrid batteries seem to be discharging and charging correctly.
     
  16. Samuel Williams Jr

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    Compression being good is great, so it has to be something else?
     
  17. privilege

    privilege Member

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    nah, that can't be. aerodynamics are bogus marketing hype n stuff
     
  18. TMR-JWAP

    TMR-JWAP Senior Member

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    If you think the downstream O2 sensor is creating a problem, just disconnect it where it plugs into the car harness. See if mpg changes. You'll get a CEL due to the open circuit, but at least it will be a constant open circuit and the car will recognize and adjust for that.

    What was the source for the remanufactured engine? Are you certain is was built for a prius? (cams, etc). It sure sounds like it's an engine power problem, specially the part about struggling to go uphill. Air intake, fuel and exhaust. One of the three isn't right and is holding the engine back.

    I would also check the temperatures of all four wheels after a good drive. They should be slightly warm, but not hot. Any that have a brake dragging will be significantly warmer than the others. I don't think the Gen 3 suffers as much as the Gen2, but if you have a leaky brake system/actuator, it may be applying slight pressure to one or more of the brakes. I'm experiencing this exact problem right now with a 2005. It appears it's leaking actuator is causing a bit of pressure on the driver side front brake, and that wheel is quite a bit warmer than the other three. This car is getting around 33 mpg. I haven't totally dug into it yet, but that is my main suspicion. That wheel's brake pressure sensor was also showing a point or two higher on techstream when the car is just sitting.
     
    #18 TMR-JWAP, Apr 30, 2021
    Last edited: Apr 30, 2021
    Tim Jones likes this.
  19. Tim Jones

    Tim Jones Active Member

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    That was supposed to be a joke.
     
  20. Chardone69

    Chardone69 New Member

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    It’s not the brakes and the engine is for a Prius. I’ve bought many motors from this company through the years as I’m a retired mechanic. I’m thinking it’s something to do with the transmission or the generator or just the inverter water pump not working. I don’t see any movement in the tank at all. Motor runs like a charm. Going up hills it screams like a little girl that had her birthday taken away. Has no pickup like it should either. Just a slug until you get her moving and set the cruise. Then she runs fairly well. Just the motor is always doing all the work unless your going 40 mph or under. My Camry hybrid run off the generator/battery at 70 mph and it doesn’t struggle doing anything. I’ve driven other Prius’s before as a mechanic and don’t remember any of them being a slug like this one. I really like the car and would just like to find out what in the H is going on.
     
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