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Transmission Jerking Badly in ECO Mode

Discussion in 'Gen 3 Prius Main Forum' started by dc101, May 10, 2021.

  1. ASRDogman

    ASRDogman Senior Member

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    You can put a 12v source right to the fan, if it runs, the fans okay.
    Then check for voltage at the wires when the other fan is on...


     
  2. dc101

    dc101 Junior Member

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    Good to know that I can use 12v source (sometimes the induction motor fans have a control unit which requires PCM signal from ECU). Since both the fans in Prius are supposed to be operating with AC on, I guess it further narrows down issue for me - seems like other fan is also end of life. Hopefully, fans are easier to remove.
     
  3. Mendel Leisk

    Mendel Leisk Senior Member

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    There’s no need to disconnect the throttle body coolant lines though; they have enough slack that you can lift off the body and tie to something, say inverter cables. More info, including TB torque values (in attachment):

    Bad Flywheel | PriusChat
     
  4. Mdv55

    Mdv55 Active Member

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    Is the car actually running hot? Do you monitor coolant temp?

    It sounds like you do have a fan issue but those are more for airflow for the a/c when stopped and should be unrelated to misfires and head gasket issues until you start talking rare situations.

    Since the Prius engine doesn't run when stopped they don't help coolant much. Unless you're in an extremely hot environment, once you're moving at 20+ mph there should be sufficient airflow to keep engine coolant in check. Those fans will kick on with very high, relatively for a Prius anyway, coolant temps. If you're seeing those kind of coolant temps regularly the fan issue is a secondary problem, not the primary one.
     
  5. rjparker

    rjparker Tu Humilde Sirviente

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    It might be better to check the fan connector for voltage rather than independently power them up. My observation is the fan will operate once the coolant temp gets around 200f which then quickly reduces the temp.

    Since I am in Central Texas, the ac runs most of the time along with both fans. They do fail and a failure is not healthy for the engine. They are not the easiest thing to change and most aftermarket units are questionable.

    I changed mine proactively and still have the original oem model in my garage. This is the model that was recommended by an independent Toyota mechanic. The v has an enhanced ac system. Not sure if the fans are the same on a standard Prius. Brand is UAC (Universal Air Conditioner).

     
    #45 rjparker, May 18, 2021
    Last edited: May 18, 2021
  6. dc101

    dc101 Junior Member

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    How can I monitor the coolant temp. Is there a special menu I need to go to or need advanced OBD scanner.

    The reason I suspect engine running hot is because I remember seeing "thermometer" symbol turning on for a few seconds and then went away. I thought it was due to low coolant level. Again, just pure guess - no temp gauge (not sure with all the sophisticated electronics, why Toyota skipped on temp reading).

    I am going to get voltage readings on the fan connector this evening once I get home.
     
  7. Grit

    Grit Senior Member

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    because it wouldn’t be safe to keep our eyes in the temp gauge and not on the road. You can get a scan gauge and avoid larista monthly fees, it’s all marketing hype.
     
  8. Mdv55

    Mdv55 Active Member

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    Scan Gauge is one option or you can get a Bluetooth OBD2 port adapter for $20 and monitor all sorts of things through the Torque app on your phone.

    Toyota skipped the temp gauge on the Prius because it's cheaper and because coolant temp goes all over the place on these cars. The average Prius owner would freak out since they seem to have little understanding of most things mechanical.
     
  9. dc101

    dc101 Junior Member

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    What temperature range should I be expecting. This evening I will test out temp and also the fans.
     
  10. Mdv55

    Mdv55 Active Member

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    My car runs at 195 at highway speeds. Will spike to 200 climbing hills oraccelerating under heavy load. Highest I've seen is 203 pounding up a long hill at 85mph.
     
  11. ChapmanF

    ChapmanF Senior Member

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    Generally, the numbers come out more nice and round in celsius (almost like the engineers were choosing setpoints in celsius, or something!).

    The thermostat usually begins opening around 83℃ and should be fully open around 85℃. If the engine is warming up, below those numbers the temp should rise at one rate, and then when it gets in that neighborhood slow down. Probably doesn't go much over 85℃ unless there's real work being done. I'm pretty sure the fans come on around 95℃. If you see the temperature heading up to that value, it often stops, or turns around and decreases again, once the fans come on. At least that's what I'm used to seeing.
     
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  12. rjparker

    rjparker Tu Humilde Sirviente

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    195f normal fully warmed up peaking around 205f. The fans will quickly reduce the 205f back to ~195f.

    After the engine shuts off with the system remaining in Ready, the temp may drop slowly down to 155f depending on how long the engine stays off. When the engine starts again temperatures will rise back to 195f.

    This is normal thermal cycling of the engine and is a reason why long waiting or camping in Ready mode is not good. With the ac on, the hv battery will drop faster making the engine cycle quicker, therefore reducing the magnitude of thermal cycling.

    Pic from video capture of obd2 monitor:

    6A68F822-7C70-495A-94F6-074EB673701C.jpeg
     
    #52 rjparker, May 18, 2021
    Last edited: May 18, 2021
  13. burebista

    burebista Active Member

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    If it helps, temperatures from a 200 miles trip a couple of days ago.

    Screenshot_20210518_205619_priusfan.info.bthsd10.jpg
     
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  14. cnc97

    cnc97 Senior Member

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    The only way mine will reach 205 is sitting parked in maintenance mode. If I’m moving, it (summer may change that) doesn’t get hotter then 188-191
     
  15. rjparker

    rjparker Tu Humilde Sirviente

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    This is up a steep grade in the summer. Inspect the pics carefully at the bottom.
     
  16. cnc97

    cnc97 Senior Member

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    I saw that. Even going to Chattanooga last year I don’t think I even broke 200. But I get to find out in about a month.
     
  17. dc101

    dc101 Junior Member

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    Thanks for all the information regarding temp ranges. The second fan issue is resolved - seems like something was loose when I pulled the airbox assembly. I checked the fans on with AC before I left train station for home. No drivability issues so far. I have iCarsoft MB II when I used to own S430. I will try that for reading deeper info - not sure if would as they have JP model for Japanese. I will report my findings.
     
  18. ASRDogman

    ASRDogman Senior Member

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    So the fan connector was loose? Or a sensor wire for the fan???
    They are both working now?

     
  19. dc101

    dc101 Junior Member

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    I think connector was loose. I just shook wires and both fans are working (one is relatively noisy). I monitored temperature and it never went above 90 degrees.

    Here is the dilemma. I drove car this evening (4 hrs after being parked) . It again acted up - engine trying to catch up as soon as began driving (low speed). Anyway, I continued driving following my typical driving pattern. At low speed when trying to accelerate, the engine multiple times hesitated trying to catch up, car shaking and then smoothing out. So, obviously problem is still there - just manifests itself at random times. BTW, no codes setup so far.
     

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  20. dc101

    dc101 Junior Member

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    Update: I drove the car this morning. Right at the beginning it was misfiring. Drove a little bit further near my home, and P0301 error showed up. I have new NGK plug for all cylinders, coils were swapped between Cylinders 1 and 4. So, the issue is consistently coming with Cylinder 1. During my 6 mile stop and go round trip, I experienced misfiring about twice.

    Not sure what should done at this point - I do have Intake manifold on to-do list this weekend. However, should I be looking at a new engine or head gasket rebuild (I will need a mechanic). What is recommended. Based on the rebuild videos, it seems like lot of moving parts for a mechanic as well - causing potential future problems?
     
    #60 dc101, May 19, 2021
    Last edited: May 19, 2021