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Idles roughly until accelerator pressed

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by ETPrius, Sep 9, 2019.

  1. ETPrius

    ETPrius New Member

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    07 Prius with about 180,000 miles. The engine shakes badly and has a knocking sound on startup and while idling. If the accelerator is pressed slightly the engine smooths out.

    I have replaced coils and plugs, cleaned the MAF sensor with proper cleaner, but the engine still runs rough.

    The fuel injectors were replaced with new ones a few years ago.

    All the old plugs had oil on them and a couple were badly burnt.

    Any thoughts on what I should check next?
     
  2. jb in NE

    jb in NE Senior Member

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    Did you check the throttle body for carbon build-up?
     
  3. ETPrius

    ETPrius New Member

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    I’ve cleaned the throttle body in the past and checked it recently. No visible build up although I do see oil pooled at the bottom.

    The engine knocking sounds are violent. But it does cease when giving a bit of fuel.

    Unfortunately I could not read the engine codes to see if the misfires are no longer present.

    Would dirty fuel injectors be a potential cause? I put new injectors in about 3 years ago.
     
  4. Skibob

    Skibob Senior Member

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    By new do you mean factory new, China aftermarket new, or eBay rebuilt new?
     
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  5. ETPrius

    ETPrius New Member

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    NAPA Echlin Part #: CRB 238724
     
  6. Skibob

    Skibob Senior Member

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    So China aftermarket new. You could get a set of rebuilt factory ones on eBay and see if that helps.
     
  7. Patrick Wong

    Patrick Wong DIY Enthusiast

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    I suggest checking engine compression.
     
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  8. ETC(SS)

    ETC(SS) The OTHER One Percenter.....

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    +1

    What's your oil burn rate?
    Did the knocking and shaking change after the plugs and coils?
    Have the plugs ever been changed before?
    Did you check the PCV valve?

    The compression check will say much, but if all 4 holes are normal and have good compression, then you might have to go back and check over some of the stuff that you've already replaced.

    My 06 (non-Prius) started stumbling on idle at 120,000 miles, so I cleaned the MAFS, changed the plugs and coils and cleaned the TB - which was medium dirty and the original culprit.
    The thing is.....I introduced another problem (coil pack) while troubleshooting the original problem.
    It tool me a little bit of time to figure everything out which I did when I reinstalled the original coil packs.

    Good Luck!
    Let us know how it winds up.
     
  9. SteveLee

    SteveLee Active Member

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    Any updates on this issue. My son has the exact same thing you are describing and has done the same fixes with no luck. The thing he has not done is the compression test. And he is losing some coolant, though that could be from a weak coolant reservoir cap? After changing the coils the problem disappeared for a month or so, then returned. His is a 2014. Now my 2010 is starting to show signs now and then.
     
  10. Skibob

    Skibob Senior Member

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    Well a 2014 is a gen 3 so the problem would best be solved in the Gen 3 forum. General consensus will be a blown head gasket with the coolant loss.
     
  11. ETPrius

    ETPrius New Member

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    Sorry for the slow reply, thanks for responding. This is my dads car so it took a while to get the answers. And I was just able to check the engine codes today.

    Oil burn rate?: approx. 1 quart every 5,000 miles
    Did the knocking/shaking change?: less knocking after and it smooths out when pressing the accelerator slightly, but still misfiring
    Have plugs been changed before?: Yes, 3 years ago. When changed this time they were covered with oil and burnt.
    PCV valve checked?: that’s next. I bought a new one from Toyota and planned to replace it.

    The fuel injector replacement I did 3 years ago originally solved the problem. I also sprayed the MAF sensor with proper cleaner and cleaned the throttle body at that time.

    I cleaned the MAFS again this time and checked the throttle body which didn’t look too bad.

    Just checked the codes again. Random misfires on cylinders 1, 2 and 4. P0301, 302 and 304. That’s with new plugs and coils. What are the odds that those injectors have problems? Would the pcv valve make that much difference? Is ECM a potential problem?

    Obviously a trip to a decent mechanic for full diagnostics is probably necessary but the collective knowledge here is usually very helpful.
     
  12. ETPrius

    ETPrius New Member

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    Any more thoughts on the symptoms as described? Thanks
     
  13. Patrick Wong

    Patrick Wong DIY Enthusiast

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    My post #7 above suggested you check engine compression or do a leak down test. This is required so you can determine whether the engine is in basically good mechanical condition or not. If the engine has worn rings etc. due to poor oil change practices in the past, it will need to be replaced or rebuilt.

    Also, you mentioned that you had replaced the spark plugs and igniters. If you did not use the correct NGK or Denso iridium plugs, and if you did not install the correct Toyota igniters, that may be part of the problem.
     
  14. Mendel Leisk

    Mendel Leisk Senior Member

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  15. ETPrius

    ETPrius New Member

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    Still looking to do the engine check.

    Coil packs were Toyota parts, 90919-02240. I checked and that was an exact match with original part. Plugs were either Bosch or NGK iridium plugs from the local parts store.

    My dad has always changed the oil religiously every 3000 miles. The car only began losing oil after a dealership pulled the injectors out years ago without permission. They were instructed to put them back rather than my dad paying them $1200+.

    Wondering if the replacement injectors could be a problem again. The car ran great for a few years after changing them.
     
  16. kswahl1

    kswahl1 Junior Member

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    Did you ever get the injectors replaced?
     
  17. ETPrius

    ETPrius New Member

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    Thanks for the reply. Not yet but hopefully soon. Planning on ordering a new set of injectors and plugs from Toyota again to replace the existing parts that I replaced earlier. Also a new PCV valve. New Toyota coil packs are already in along with some other recommend parts.

    This is strange because the car ran great for a couple years after putting in the plugs and injectors. Maybe something is causing issues with the injectors.
     
  18. DeadGen2

    DeadGen2 New Member

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    In my travels here (the forum) I read up on plugs, apparently the Bosch units are garbage, kill mpg, can cause misfires. Run OE Denso or NGK I know it’s almost 40 bills, but good for 100k...


    Also, for most ICEs I’ve ever diagnosed for a rough idle (too many) the simplest test is: unplug coils one at a time, if no change in idle, that’s your culprit, in your case it’s the injectors I would unplug one at a time, since their lineage is questionable. But only after going back to proper OE plugs.
     
  19. ETPrius

    ETPrius New Member

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    Great advice. Root cause may be something else since the first replacement set was NGK purchased from a local auto parts store. And those plugs went bad prematurely. But maybe they weren't as good as Toyota source parts. I'm ordering plugs from Toyota and will also check the injectors and probably order those again new from Toyota. The fact that gently pressing the accelerator smooths out the idle seems to be a clue pointing to fuel issue.

    I don't know, the first change of plugs and injectors worked wonders. This should not be so difficult to troubleshoot. Will just have to divide and conquer per the good advice given here until it's working. Most difficult step will be checking compression.
     
  20. strawbrad

    strawbrad http://minnesotahybridbatteries.com

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    I have seen four Prius that had broken piston skirts. It's amazing that the engine will keep running with a junk of a piston missing. My current work Prius had a engine tick at idle that would smooth out with acceleration. No codes were present. The car lacked power and mileage was terrible. The cylinder with the broken piston would quickly foul the plug.

    After eliminating the other possibilities the easiest test to confirm would be to drop the oil pan and look for piston junks.