Gen2 (2006) intermittent poor engine power

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by LewisM, Apr 8, 2015.

  1. LewisM

    LewisM Junior Member

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    Our 2006 Prius (175,000 miles) has recently suffered intermittent periods of diminished ICE power. For instance, for about 1 hour recently driving a hilly section of I-81 through eastern TN, the car was struggling to maintain 68 mph and the HV battery stayed mostly drained at 1-3 bars. Gas milage was falling, but no misfire. After stopping at a rest area, it was fine. No OBD codes and ICE seems OK otherwise. Experienced a similar reduction in ICE power a few days later. Dealer has no clue.
    The only similar experience I've had with another car was when it's catalytic converter became plugged, but that was not intermittent. Any ideas?
     
  2. bisco

    bisco cookie crumbler

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    large hills can be draining. have you tackled them in the past with no problem? how are your mpg's in regular driving?
     
  3. LewisM

    LewisM Junior Member

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    Thanks for the response. I've driven this car for 55,000 miles and have carefully monitored mpg and HV battery charge. You are correct that hilly terrain can quickly drain the HV battery, but I've driven this section of I-81 several times without problem; that is, in the past I've been able to maintain 68-70 mph without the problems experienced last time. MPG averages 46-50 all the time, and the only time the HV charge has dropped below 3 bars is during longer, steeper grades. I may be mistaken, but it seems to me that the ICE output was temporarily down by 20% of so, but it recovered after the rest stop and the remaining 1500 miles on that trip were uneventful.
    Could it be the cruise control? I don't normally use it, but did this time.
     
  4. cyberpriusII

    cyberpriusII Prodigyplace says I'm Super Kris

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    I KNOW NOTHING -- so this is a WAG. Take it as you will. But we had power issues in our Camry on hills, etc. We cleaned the MAF and it really made a major difference. You might give it a try. It seems like the Prius MAF is pretty easy to get to, compared to some cars.
     
  5. bisco

    bisco cookie crumbler

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    if it cleared, might have been something in the gas. if not, or it comes back, cp.'s^^^ advice is good, and you might pull the plugs and injectors as well.

    did the dealer check the codes?
     
  6. LewisM

    LewisM Junior Member

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    Thanks for the ideas. I just cleaned the mass air flow sensor per cyberpriusII's suggestion, above, and following the handy directions at Toyota Prius: How to Clean the Mass Air Flow (MAF) Senor - PriusDIY.com. To the best of my knowledge it has not been cleaned in 175,000 miles.
    Bisco asked if the dealer checked the codes. My OBD-II code reader showed nothing, and the dealer wasn't interested in looking at the car if there was no on-going malfunction.
    Let's see if cleaning the mass air flow sensor will make any difference.
     
  7. cyberpriusII

    cyberpriusII Prodigyplace says I'm Super Kris

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    You followed the master's tutorial (Hobbit). On our Camry, at 145K the MAF was absolutely filthy. When we cleaned it, it was an immediate and powerful improvement. I suspect you may find the same improvement....let us hope so. :)
     
  8. JC91006

    JC91006 Senior Member

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    What has happened with your car is what happens often with my 2006. The HV battery pack has lost some of it's capacity and when you drive/climb a hill, the hv battery will drain if you push the pedal to the metal. Once the battery drains (1-2 bars remaining), it goes into a low power mode. The ice works harder and your mpg will be in the teens. Once the battery recovers from the low SOC, goes back up to 5 -6 bars, then your car will operate like normal again.

    A helpful member (miscrms) here helped me tackle this issue by showing me how to drive the car so that the battery will not drain all the way and prevent my car from going into low power mode. Here is something he's posted before (he has a few of these instructional posts).

    - When climbing bring up the "energy" display that shows the arrows going in and out of the battery.
    - Find the point on the accelerator where you are maintaining speed on the hill.
    - Adjust the accelerator position slightly until the energy display show no arrows into or out of the battery. (Note this can be from either lifting up a little on the accelerator, or from pushing it a little harder. If its floored though, there's only one way to go).

    I've actually been really impressed with the hill climbing ability of the Gen 2. The problem IMHO is that it does take some driver participation to avoid depleting the battery. Once you have driven it down to 1-2 bars, its game over. Now you are not only on ICE power only, but are sapping more power off the ICE to bring the battery SOC back up.

    By being mindful about what the battery is doing when you are climbing, I've found I can routinely climb long 7-8% grades at 65-75mph without dropping any bars off the battery. This is extra handy, because if you do have to slow down waiting for an opportunity to pass a truck or something, I've found that by maintain a fullish battery the Gen 2 even has plenty of power to get back up to these speeds from 35mph or under on these sorts of grades. This does mean flooring it and using battery and the engine will be at max rpm and sounds like its going to explode, but its really fine :) As long as you don't over do it and drain the battery you'll still be fine. In fact, I've often found that after one of these acceleration bursts you can find a pedal position that still maintains 65-75mph and puts some charge back into the battery while you continue to climb, just in case you have to pass again.
     
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  9. bisco

    bisco cookie crumbler

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    if this is the case, you might consider a grid charger from the priuschat shoppe.
     
  10. LewisM

    LewisM Junior Member

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    CyberpriusII was right; it was a dirty mass air flow sensor. I cleaned it yesterday and today saw a increase in MPG from 46 to 50 on the same terrain. The same long interstate grade that required battery support to maintain 68 mph with cruise control, now does not need any battery help. I do not see MAF cleaning on the preventive maintenance list, but it should be. Thanks, guys.
     
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  11. JC91006

    JC91006 Senior Member

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    You might have experienced slightly worse mpg with the dirty MAF, but that won't explain the battery SOC causing loss of power.
     
  12. LewisM

    LewisM Junior Member

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    I do not know how a dirty MAF filter hurts ICE performance. But imagine if it could reduce ICE power by 10-20%. Let's assume the ICE alone should have just enough power to manage a 5% grade without battery assist, and that the hilly section of I-81 through east TN is a series of 5% grades every mile or two. What I saw was that the ICE needed help from the battery, and battery never could fully recover from one hill before it was faced with the next.
    I may be mistaken, but it appeared to me today that a similar interstate grade (5%??) steep enough to need battery help a couple of days ago, is now within the capability of our ICE alone.
     
  13. cyberpriusII

    cyberpriusII Prodigyplace says I'm Super Kris

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    I don't know much about any of this. But, when we cleaned the MAF, our Camry was struggling to hit 35 mph on a steep hill. After cleaning, it hit 50 mph with no issue. Of course, the Camry is not a hybrid, so, not sure how that compares, but if that sensor is dirty, it sure can decrease power from the ICE.

    And, now, to make your life more complicated....have you considered cleaning the throttle body? :p
     
  14. LewisM

    LewisM Junior Member

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    Thanks, CyberPriusII, all the evidence I've seen thus far suggests that MAF cleaning is a preventive maintenance issue that has been overlooked. I don't want to be jumping to conclusions about this, but my Prius engine certainly has more HP now than before I cleaned the MAF sensor. The fact that its ICE happens to be working in conjunction with an electric motor makes do difference. I'll post again here if I discover something new. In the meantime, I'm writing to the local Toyota dealer to describe what happened.
     
  15. bisco

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    i think you're right, but maf contamination appears to come from bad gas, which seems to show up more often in rural parts of the country. something that toyota can't really account for in testing and building a maintenance schedule.
     
  16. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Actually, the MAF sensor contamination comes from dirt-laden air getting past the engine air filter and dirt particles accumulating on the sensor. I would say that this problem is caused by leaving the engine air filter in service longer than the filter is effective - or using a substandard filter. It probably doesn't help to drive on dirt roads where the car in front kicks up lots of dust.
     
  17. bisco

    bisco cookie crumbler

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    thanks, thats what i meant to say.;)
     
  18. LewisM

    LewisM Junior Member

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    I can't speak for the first owner (120,000 miles), but I've been conscientious about changing filters for the last 57,000 miles. The MAS did not appear to be dirty, but something was affecting it.

    We just drove to Louisville, KY, and back, for a total of about 900 miles, and averaged 50.4 mpg. Very pleased with that.
     
  19. cyberpriusII

    cyberpriusII Prodigyplace says I'm Super Kris

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    Glad things are looking good. I guess I have learned a few things on here in the past seven :sick: years!

    When I first posted, I could not figure out how to get the cabin filter out of the car!!

    Only problem, you are making me think I should go ahead and clean the MAF and the throttle body on my Prius....
     
  20. LewisM

    LewisM Junior Member

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    More followup: Driven about 2,500 miles (4k km) since cleaning the MAS sensor: interstate, rural, and city. Sustained speeds up to 75 mph. Multiple trips 3.5 miles up and down the mountain on which we live. Average 50.7 mpg. Previous average was about 46.
     
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