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Poor Idle is driving me crazy!

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by vertex, Jun 7, 2009.

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  1. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Knowing that the engine ECU is impaired, IMO you are wasting your time by pursuing these other avenues. I've removed the engine oil cap on my 2004 and that had a tiny effect on idle speed. Hence you'd have to have a huge leak to make a difference in engine performance, assuming no other problems exist.

    I understand that you are reluctant to accept that the ECU needs to be replaced due to the cost.
     
    #41 Patrick Wong, Jun 12, 2009
  2. dogfriend

    dogfriend Human - Animal Hybrid

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    OP could perform your experiment in reverse - remove oil cap, look for tiny effect on idle speed - if no effect on idle speed, then huge leak already exists.* :madgrin:















    * Impaired function of ECU may make this test invalid. :madgrin:
     
    #42 dogfriend, Jun 12, 2009
  3. vertex

    vertex Active Member

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    I've come to the conclusion the ECU is scrambled. All the sensor signals seem OK when I check them on the Autoenginuity. Does anyone know how much this costs to replace at a dealer? If I buy a used one, how much would I be charged to install it. I understand it needs to be programmed, can I get it programmed and put it in myself?

    Another crazy idea that I had was that I noticed that if i partially block the MAF, it seems to behave properly, at least at idle. I was thinking of remapping the sensor, based on normal mapping except when in idle, lower the gain.

    Thanks for your thoughts, they have been helpful.

    Howard
     
    #43 vertex, Jun 14, 2009
  4. dogfriend

    dogfriend Human - Animal Hybrid

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    I would give

    http://autobeyours.com/PriusParts.htm

    a try. If you get an ECU from the same model year, I'm not sure why you would need any programming, but I haven't looked at the manual to see the procedure.
     
    #44 dogfriend, Jun 14, 2009
  5. vertex

    vertex Active Member

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    Steve Woodruff. Nice guy. Says I need a set for $1500.
     
    #45 vertex, Jun 14, 2009
  6. vertex

    vertex Active Member

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    An update. I brought the car to Westchester Toyota last Wednesday. They worked on the car yesterday. They said there is not a vacuum leak, and cannot figure it out yet. I suspect on Monday they will come back with the ECU, but so far, everything they checked looks OK. They said they would charge up to 3 hours of shop time, so so far I expect a minimum bill of $296.
     
    #46 vertex, Jun 19, 2009
  7. jayman

    jayman Senior Member

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    Oh, sounds like fun. Sometimes diagnostics are worse than a murder mystery
     
    #47 jayman, Jun 20, 2009
  8. vertex

    vertex Active Member

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    The car has been at the dealer over a week. Thursday they called me and said the problem was the TPS. I was quite skeptical of this diagnosis, but had them change it. Of course, it did not fix it. I have lost confidence in them, and will take the car back as soon as I can get over there this week. I am going to try to fix or replace the ECU.
     
    #48 vertex, Jun 27, 2009
  9. jayman

    jayman Senior Member

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    Of course, you still had to pay them ...
     
    #49 jayman, Jun 28, 2009
  10. vertex

    vertex Active Member

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    Well, got the car back. It was running worse then ever! The dealer couldn't figure it out, so there was no charge! The dealer ran diagnostics on the computer, and found nothing wrong. My plan is to pull the computer and see if I can fix the 5 volt output. (Does anyone have schematics for them?) We'll see if that helps, if I can fix it. If that doesn't help, I think remapping the MAF will do the trick. Anyway, it is worth a try before replacing the ECU.
     
    #50 vertex, Jul 2, 2009
  11. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Here's my suggestion: buy a used engine ECU from eBay. There are many on sale for $200 or less:
    prius engine ecu, great deals on eBay Motors on eBay!

    If the engine ECU is the only issue that your car has, I believe that the car will start when you replace the ECU, although DTC P0630 will be logged. Then drive the car to the dealer and ask for the VIN to be entered into the engine ECU. That might cost you another $100 or so; however for ~$300, you can be done with this saga.

    Its not surprising that the diagnostics would not yield much help, if the engine ECU can't even provide 5VDC output.
     
    #51 Patrick Wong, Jul 2, 2009
  12. vertex

    vertex Active Member

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    The 5volt output is only for the sensors. I don't believe it is used internally, at least not the exact same 5 volts, since the sensors do work, and they seem to have the correct output range.
    I thought you could not start the car at all. However, if only a DTC is triggered, then maybe I will change my priorities.
    Thanks.
     
    #52 vertex, Jul 2, 2009
  13. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Assuming that the engine ECU is the only fault that your car has, I think it is worth buying a salvage unit and replacing it yourself. DTC P0630 "VIN Not Programmed or Mismatch" does not appear in the table of DTC that will result in the ECM entering fail-safe mode. Hence my belief is that this DTC by itself will not prevent the engine from running.

    If I'm wrong then you'll have to have the car towed to the dealer. However this plan provides a reasonable and relatively low-cost way to resolve the known bad engine ECU issue. Good luck.
     
    #53 Patrick Wong, Jul 3, 2009
  14. vertex

    vertex Active Member

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    OK, I fixed it! It was NOT the ECU. The TPS needed to be adjusted a little below spec, at 11% to work. I had tried adjusting it before, but it would never go below the 13.5% specification. I took off the TPS and bent the tabs to increase the rotation CW of the TPS at the stop. I drove it about 20 miles this afternoon, and all was well. Thanks for all your ideas and support. I now need to get the AC charged up. If I can find the bottle of oil I bought that went AWOL, I hope to get that done this weekend.
    My next BIG project is plug in conversion. I do not plan on purchasing one, this will be a strictly DIY project. I'll comment more about that in the correct forum.
    Have a great fourth!
     
    #54 vertex, Jul 3, 2009
  15. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Congratulations for making the car run, even with an ECM that is off... Let us know when you pass emissions inspection.

    Also, after you've logged a couple thousand miles, pls tell us what mpg you are realizing (computed by taking change in odometer reading divided by number of gallons purchased.)
     
    #55 Patrick Wong, Jul 4, 2009
  16. vertex

    vertex Active Member

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    I passed inspection yesterday, no problems. I drove the car 110 miles on Sunday, and and got 47.2 MPG on the MFD. As an aside, I drive 2.2 miles to the train station to go to work in the morining, and can make the trip in EV mode. (It is kind of cheating, in that it is mostly level and downhill. I could not go 1/4 mile back in EV, it is up hill.)
     
    #56 vertex, Jul 7, 2009
  17. Patrick Wong

    Patrick Wong DIY Enthusiast

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    That's excellent, sounds like you've successfully resolved that problem. Nice to know that you can finally enjoy driving your salvage vehicle. Good work!
     
    #57 Patrick Wong, Jul 7, 2009
  18. jayman

    jayman Senior Member

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    Sometimes you have to give it the old college try. Very obvious that as the fleet ages, most dealerships won't be any help
     
    #58 jayman, Jul 8, 2009
  19. vertex

    vertex Active Member

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    Love the car. What a journey! I have started a new thread under PHEV conversions.
     
    #59 vertex, Jul 8, 2009
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