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Odd running following throttle plate cleaning.

Discussion in 'Gen 2 Prius Main Forum' started by DMC-5180, Sep 30, 2017.

  1. DMC-5180

    DMC-5180 Active Member

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    Today It was a beautiful day here, so I thought I’d do a little maintenance on my 05. I decided to clean the the throttle plate bore as I’ve seen talked about on here. Mind you the car was running fine and predictable before starting this.

    I pulled the air box off and could see the throttle plate was dark with crud.

    I happened to have an old tooth brush and a can of gumout carb an choke cleaner along with a can of starting fluid.

    I started with a little starting fluid sprayed on top of the closed plate, then used a paper towel to wipe up what I could. Then I switched to gumout. It did a better job dissolving the oily crud. After I was done, I put everything back together and started the car letting it idle through warmup and ICE off. I cleaned up my stuff then took it for a short drive, 6 miles or so. As I’m pulling back into my neighborhood after 5 miles I notice the ICE not shutting off when I Let off the pedal. When I pull into my driveway the engine continued to run at an oscillating idle.

    I raised the hood with the engine continuing to run. I reached down to check the throttle shaft (return spring side) it appeared to be fully closed. I manually rotated it to see if the rpm would increase, it did but the idle control seemed to fighting the rpm increase.

    Mind you there was a puddle of liquid in the intake before I left to test drive, but I figured it would get sucked through the engine quickly enough under normal driving that wouldn’t be an issue.

    So, any suggestions as to what might be going on?
     
  2. edthefox5

    edthefox5 Senior Member

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    That's not how you clean a throttle body. You don't use paper towels and you don't hose it down with carb cleaner as all that cleaner gets sucked up in the intake and the engine is forced to ingest it and burn it off.
    Should have used a long strips of cloth. Push strip of cloth in and hose it down with cleaner and use cloth to scrub the throttle body. Pull strip out and discard, that way all that nasty and very dirty carb cleaner does not get into the cylinder. Repeat with the cloth strips till they are clean when u pull them out,
    Lubricate the throttle shaft spring and make sure you tighten the 10 mm
    Throat clamp under the air cleaner. If not unmetered air will sneak by the maf and the engine will not be happy.

    Edit-Forgot another important part and thats pulling off the back hose on the TB thats the one connected to the pcv valve. With hose off and cloth in the bore hose out that hose connector so its open to the tb body. Lots of black gooey crap there.While the pcv hose is off take a look at the end and see if its getting clogged. If you run dino oil it will be alot sludgier than if you run synthetic oil especially if your running dealer vat oil Yuck...thats some cheap oil...
     
    #2 edthefox5, Sep 30, 2017
    Last edited: Sep 30, 2017
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  3. JC91006

    JC91006 Senior Member

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    Disconnect the 12v battery for a minute. It should be fine after
     
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  4. DMC-5180

    DMC-5180 Active Member

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    Fair enough, but to late for that now. As far as tightening the clamp goes. I’m fairly positive it is secure tight. Btw I did not drown it. I sprayed the cleaner into a jar and dipped the toothbrush into it then opened the throttle plate fully and scrubbed caked on stuff loose. Only after, did I give it a quick rinse to wash things clean. Yes there was a puddle in the intake but not bad, plus there was a small puddle of oil in bottom of the intake before I started.

    Anyway, I took the car out for a 30 mile drive too see if things would self correct. It did appear to help, but I don’t quite know if it is completely back to normal yet.
     
  5. DMC-5180

    DMC-5180 Active Member

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    What does disconnecting the 12v do for me? It did not throw any MIL codes yet. But I can check to see if I have any are pending after the 2 drives I took.
     
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  6. JC91006

    JC91006 Senior Member

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    It lets the car relearn the throttle setting
     
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  7. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Also, you should not manually rotate the throttle plate when the Prius is READY, as you are fighting the throttle motor.
     
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  8. DMC-5180

    DMC-5180 Active Member

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    Ah, that makes sense.

    Actually it didn’t move much.
    But when the throttle seemed like it was closed. The idle oscillation seemed pretty weird though. But the most puzzling was that the ice wouldn’t shut off.

    Manually shut the car off then waited a little bit and repowered it up the ice started up but at a much higher rpm for a moment then settled back down to idle hunting but still didn’t shut down.
     
  9. edthefox5

    edthefox5 Senior Member

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    You can put it in Inspection mode it does a high idle quite steady until you shut it off.
    Search Prius Inspection Mode on youtube for the correct button pushes to get it in that mode. I can't remember.

    There's always a puddle of oil on the bottle of the throttle body. Heard its becasue Its a byproduct of it unique Atkinson-cycle which its post combustion ratio is different from its effective combustion ratio.... or maybe the engine has a very high engine vacuum and its just sucking alot of pcv gases and it forms a puddle. But its always there.
     
  10. DMC-5180

    DMC-5180 Active Member

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    Yeah, I’ve never tried doing the dance to get to inspection mode. If I want the engine to run I just turn HVAC on. The ICE will just start running and stay on.
     
  11. Mendel Leisk

    Mendel Leisk Senior Member

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    I've disconnected the 12 volt for safety when working on the brakes, and have noticed subsequent revving up after startup, just momentarily. It definitely is doing something unusual.

    This is on 3rd gen for what it's worth.
     
  12. DMC-5180

    DMC-5180 Active Member

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    To clarify, all cleaning was done powered off. When I did try to move the throttle in READY, the engine was Running as opposed Ready and waiting to start. But I get that you should avoid rotating the throttle plate while powered. After all it is drive by wire system as opposed to the good ole days of a manual cable.
     
  13. edthefox5

    edthefox5 Senior Member

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    It shouldn't. Engine only runs usually if cats are cold or hybrid battery in purple. If your hybrid battery is in purple all the time usually the hybrid battery is getting very old and will need replacement.
    If you have the original hybrid battery it's probably on its way out given its age.

    What are you chasing with the throttle body cleaning?
     
  14. DMC-5180

    DMC-5180 Active Member

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    I generally drive with the consumption screen showing.

    I watch the Active level Scale move up and down. Under normal circumstances if the scale tops out I know the ICE is off when I have my foot off the pedal or am coasting to a stop or down hill with adequate momentum to be regenerating.

    What I was seeing yesterday following the cleaning was that the ICE was not shutting off during the same situations where it normally would. The active scale would only go to 75-90. Meaning the engine was still running with my foot off the pedal. When I pulled into my driveway, I switched to the energy screen to see the battery level. It was 1 bar GREEN, the ICE should have been OFF (trying to use up the excess energy) as I rolled in, yet it continued to run.

    I don’t have an issue with it running in purple unless I leave the car powered up and walk away from it, then it will draw the battery down to purple over an extended period. If that happens I just go for a drive and after 4-5 miles at highway speed the level will be back up to the normal level and steady.
    That’s a fairly rare event. My car gets driven on 289 mile drives every 3.5 days. Its a long weekly commute to my Work. The days I am at work my daily mileage is 25 RT from where I stay when there.
     
    #14 DMC-5180, Oct 1, 2017
    Last edited: Oct 1, 2017