Engine straining. Lost power. Poor MPG

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by AG2012, Dec 22, 2014.

  1. Easy Rider 2

    Easy Rider 2 Senior Member

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    Bad. VERY bad.
    You are probably on the verge of not starting with those readings.

    And yes, absolutely.

    I hope it reads over 13 in READY mode (ON).
     
    dolj likes this.
  2. Eclipse1701d

    Eclipse1701d Prius Enthusiast

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    You will need a new battery anyway. You might as well swap it out before you bring it to the mechanic. It just might be the Christmas miracle you are looking for! Anything under 11.0 in sitting mode is toast.

    And, with a battery that low, you may get erroneous codes, which is the last thing you want when it is in the shop...
     
  3. bisco

    bisco cookie crumbler

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    bad 12 volt can easily eat up your mpg's, not sure i've ever heard a bout a power problem before though.
     
  4. dolj

    dolj Senior Member

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    Absolutely 100% second all three sentences.

    Some say a bad battery has no effect, some say it does. I'm in the camp that says it does.

    However, in saying that, replacing the 12V is no silver bullet to fix all your fuel efficiency woes.

    My firm belief is that 12V battery health is but one factor and the overall problem of low MPG's is a lot of little things that, on their own, don't amount to much, but when added together contribute to frustratingly lower MPG figures.

    My top 5 list would be:
    • Tires--should be LRR and are not.
    • Tire pressures--under-inflated, suggest 39F/37R.
    • 12V battery--needs to be in good health and fully charged as much as is practically possible.
    • Use the correct oil--fully synthetic 5W30 or 0W20. Oil change interval can be increased to 10,000 mi/15,ooo km on synthetic. Don't overfill.
    • Loose nut behind the wheel--adjust driving to economical style.
    There are other factors, but paying attention to these 5 things should show a measurable benefit.
     
    #24 dolj, Dec 23, 2014
    Last edited: Dec 23, 2014
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  5. 200Volts

    200Volts Member

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    It is your catalytic converter. The farting sound, or puff/pop sound is the dead give away. I've gone through this twice on my 06. You'll notice it trying to go uphill, especially after the hybrid battery is down to the last bar, so it's all up to the ICE. With less hp from the ICE, the hybrid battery won't charge (maybe at all). Mileage drop to the 40mpg range, or less, is in line with my experience (at 350k miles). Mine got so bad I couldn't go faster than 67mph on the flat.
    Yes, you can visually inspect the cat. It starts white, and turns black as oil fouls the first honeycomb section (restricting your exhaust). BUT, at your low mileage you should not have had a rusted muffler, no way. Do you have water (or ?) leaking into your exhaust?
    To remove the middle exhaust and reinstall takes 2 hours, leisurely pace, when system is not hot:
    BLOCK rear tires, plus use emergency brake!!!
    ON A FLAT SURFACE, jack up front-install 2 jack stands
    Remove 2 bolts from rear exhaust section, buy rear axle, on right side, before the muffler
    Loosen all 4 bolts on cross member, remove 2 on right side of vehicle
    Remove 2 rubber hangers
    Remove O2 sensor, use DB or penetrating oil to loosen.
    Remove 2 bolts at front, to exhaust manifold. Use a 18" extension, with flex joint at the socket. Reach up at 45 degrees from rear side of the frame/cross member (below these 2 bolts). A 1/2" drive socket will give you the leverage.
    Remove pipe, inspect with flashlight for black/foulded catalytic converter intake. No solvents I've tried will clean this mechanical fouling. The honeycomb is fragile, and is about 2 inches deep, with about a 1 inch air space to the next honeycomb section.
    Replace in reverse order. Reuse fancy gasket to exhaust manifold.
     
  6. juan_dgo

    juan_dgo Junior Member

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    I'm having the same problem on my 2004 prius. Does anybody knows if replacing the catalytic converter takes care of poor engine performance? My car has gotten so bad that I can't go faster than 65mph on the expressway if I go faster it will shut down. Hybrid battery only shows 1 or 2 bars when I drive at that speed.

    Thanks
     
    #26 juan_dgo, Mar 25, 2015
    Last edited by a moderator: Mar 25, 2015
  7. Easy Rider 2

    Easy Rider 2 Senior Member

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    Only if it is plugged up and is the cause of the problem.
     
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  8. 200Volts

    200Volts Member

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    Yes, when my cat was plugged the battery would not charge like normal. This made driving up long hills even worse, as there was very little assist time from the electric motor. Replacing the cat on mine fixed the problem, but only for about 45k miles, then it started to plug again.

    In theory, in an emergency - stranded situation not on public roads, you could remove the exhaust pipe, drill a dozen 1/4" holes in the first section of the cat, and be back on the road if you have an oil fouled cat. However, this then permanently kills the cat, and you cannot get rid of the yellow check engine light until you put on a new cat. This may also eliminate the possible of trading in your old "core" cat for a new one. I do not endorse or promote this idea, do not do it, all risk is yours.
     
  9. Easy Rider 2

    Easy Rider 2 Senior Member

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    Which is to be expected if you do NOT look for and fix the underlying problem that caused it to go bad in the first place.
     
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