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I made it better and worse at the same time, please help.

Discussion in 'Gen 2 Prius Main Forum' started by Prius92, Jul 2, 2022.

  1. Prius92

    Prius92 Member

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    MPG had been going down for several months.
    Finally decided to take all the spark plugs out.
    Cylinder 1's spark plug was very wet and fuel smelling. The other 3 were worn, but fine. Decided to replace all since they already had 60k miles on them.
    Suspected sticking open injector.
    Note: I put several cans of FI cleaner in the car including Berryman's B12 and Techron with no help.
    Bought new injector.
    Had a hell of a time getting the rail back on because it kept leaking, Toyota in their "wisdom" put the metal fuel line under the valve cover, "locking it" unless you remove the cover. I learned this the hard way and the metal pipe was lifting on the rail enough to make it leak.
    Not to mention..they use Phillips screws to hold the MAF sensor on and the throttle body cover. Why the hell was that approved by engineering? You don't use soft Phillip's screws in engine bays. They should of been socket head or Torx.
    Anyway....
    I also had a hunch the intake manifold was leaking and I was partially correct, there was some bubbling of the gasket that looked like it might of been leaking slightly.
    Get it all back together and it runs much better at regular speeds, but shudders like hell at idle.
    Had a DTC for the MAF sensor. Took it back out and cleaned it liberally, and put it back in and cleared the DTC and reset the ECM by battery disconnection.
    Drove it 15 miles and the DTC did not reappear, nor was it pending per my scanner.
    But it still shudders badly.
    I've never seen an engine in an OBDII car shudder like this and not throw a code.
    Not only does it shudder, it revs up and down.
    I took the air box off, checked all the vacuum and coolant lines on the throttle body, PCV valve, etc.
    No issues.
    Plugged my scanner back in and checked for misfires. None counted.
    I'm at a loss.
     
  2. TMR-JWAP

    TMR-JWAP Senior Member

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    Sounds like a significant vacuum leak
     
  3. Prius92

    Prius92 Member

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    Where can I find a diagram for the hoses on the throttle body? I'm wondering if I might have crossed one.
     
  4. Prius92

    Prius92 Member

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    Found the diagrams, I wonder if maybe I crossed the PCV hoses?
    It did finally throw another MAF code and lean code, which indicates air leaks.



    [​IMG]
     
  5. ChapmanF

    ChapmanF Senior Member

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    I don't know if that would be easy to do given the shapes of the hoses, but it would definitely result in a large vacuum leak. One comes in after the throttle, and only one has a PCV valve in it.

    [​IMG]
     
  6. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    Toyota doesn't use Phillips screws in their engine bays. They use JIS, which to the untrained eye look a lot like Phillips. They are machined differently, and when you use an actual JIS driver you don't experience the "cam-out" effect which tears up the slot faces.

    It's a minor thing next to the overall problem, but if you do a lot of work on Japanese cars it can save you a lot of time and frustration.
     
    #6 Leadfoot J. McCoalroller, Jul 3, 2022
    Last edited: Jul 3, 2022
    ammdb, PriusCamper and jerrymildred like this.
  7. Tombukt2

    Tombukt2 Senior Member

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    I imagine similar to Posi Drive.?
     
  8. jerrymildred

    jerrymildred Senior Member

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    JIS:
    Screen Shot 2022-07-03 at 11.31.02 AM.png

    Those little teeth keep it from climbing out of the tapered slot.
     
  9. rjparker

    rjparker Tu Humilde Sirviente

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    JIS screws look like Phillips but can be excessively tightened without slipping. Phillips are specifically designed to cam out (slip out of the driver or bit).

    JIS drivers are great for removing regular Phillips screws but not the other way around. Trying to remove a tight JIS screw with a Phillips bit will strip the screw head most of the time.

    On my Honda CRV the small engine undercover is metal and has three JIS screws holding it on. You have to remove it for oil changes. The factory used power tools so the JIS screws are tight. Its super easy with JIS bits. Nearly impossible with Phillips bits. Phillips head bits with power tools strip the heads to the point you are using angle grinders and vise grips.

    Have some JIS bits marked appropriately in your tool box.
    796711EB-ED13-4AB9-9034-02C62D13A838.jpeg
     
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  10. mr_guy_mann

    mr_guy_mann Senior Member

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    Are the PCV hoses intact? They have foam covers and might have cracked where you can't see it.

    Another possiblity is that one of the injector O rings in the manifold doesn't seal. Mechanic's stethoscope is cheap enough, or get a length (2-3 feet) of small diameter vacuum hose- hold one end in your ear and move the other around the engine and try to listen for a loud hiss of a leak

    Posted via the PriusChat mobile app.
     
  11. PriusCamper

    PriusCamper Senior Member

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    My experience with the revving up and down is a failed throttle position sensor and the error code for that sometimes takes a little while to show up... As for the phillips head screw in the engine bay, it's a plastic on plastic part with an o-ring and phillips screws are pretty much standard in situations like that.
     
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  12. Prius92

    Prius92 Member

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    I took the throttle position sensor out when I cleaned the throttle body as I didn't want anything plastic or electrical to get damaged.
    I aligned it the best I could, using the "shadow" left by the screw heads, but oddly it has oval screw holes and can be adjusted.
    I've never seen a TPS that can be adjusted.
     
  13. PriusCamper

    PriusCamper Senior Member

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    It can't be adjusted without specialized calibration equipment so if you adjusted it to something different than it was already set at it could be a problem and have yet to see anyone other than the manufacture do the adjusting. Don't think Toyota techstream / dealership can adjust it either. Maybe @ChapmanF or @Elektroingenieur have more details?
     
  14. Prius92

    Prius92 Member

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    Freaking wonderful...if it can only be set at the factory, why even make it adjustable?
    That might explain why you can't order the TPS from RockAuto or car part places like Autozone...
    I'd have to find another one at a JY..because I'm sure as hell not spending $250-$300 on a new one.
     
  15. PriusCamper

    PriusCamper Senior Member

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    I bought one at a junk yard for like $35... Works great...
     
  16. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    car-part.com lists a number of "throttle body/throttle valve housings" in Iowa junkyards for $35 & up

    Confirm that it is the correct part, since they use generic names for all parts & assemblies.
     
  17. Prius92

    Prius92 Member

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    I'll see what Toyota charges and what a JY charges. The closest JY near me is a rip off yard, they want more for used parts than you can buy them for new.

    So it can't be adjusted using a DVM? You'd think it would be adjusted at closed throttle to a baseline voltage from the 5v reference signal.
     
  18. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    I think I'd expect that too, but I've never dealt with this on a Prius. Have you rented the official repair manual for consultation?

    I had a Subaru from that vintage which calibrated itself. It would idle like crap for a half hour or so, sometimes even stalling. But once it learned, it was good until the next 12v blackout. I don't know if Toyota has ever done anything like that.
     
    #18 Leadfoot J. McCoalroller, Jul 3, 2022
    Last edited: Jul 3, 2022
  19. PriusCamper

    PriusCamper Senior Member

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    Maybe one of us could pull one at a junk yard near us and mail it to you? If you can find a Prius that's only been on a Pick 'n Pull lot for a day or two and then message the location here and we'll see who's near that location?
     
  20. Elektroingenieur

    Elektroingenieur Senior Member

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    The Repair Manual (more info) includes, in the procedure for diagnostic trouble codes P0120–P0123, P0220–P0223, and P2135, a graph of throttle position sensor output voltages VTA1 and VTA2 for various throttle valve opening angles, but—as I mentioned in another thread—there’s no published procedure for adjusting the sensor.

    The inspection procedure is limited to DC resistance measurements between various terminals of the sensor’s four-position connector. If any resistance isn’t as specified, the throttle body assembly and its non-reusable gasket are replaced.

    Parts catalog reference: Figure 22-11, Fuel Injection System.
     
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