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Loss of power - fuel filter, coils, other??

Discussion in 'Gen 3 Prius Technical Discussion' started by RyanFlorida, Aug 26, 2016.

  1. RyanFlorida

    RyanFlorida Member

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    I have been having an ongoing power loss problem coupled with low gas mileage around 40 MPG on my 2010 Prius. It has 160K miles, it is from Texas and seemed to have been a business owned car for most of it's life. Spark plugs were recently replaced and coils tested ok on a multi meter. Mobil 1 0W-20 Full Syn oil regularly.

    The power loss feels like a slow flowing fuel filter, in that I really have to press all the way down on the pedal to get good acceleration. Another example is I was driving up a relatively tall hill going about 35 MPH and to gain speed I need to have the pedal nearly to the floor or all the way in to the PWR section of the accelerator display. When I was in the ECO section of the accelerator display I was loosing speed going up this hill. I have owned a 2012 Prius in the past and have driven that same hill without problem or power loss. I have driven other vehicles with poor acceleration and have changed the fuel filter to regain acceleration.

    Being that the Prius has an integrated fuel filter, should I still change it? Those of you who say it is a lifetime filter, what is the lifetime? The tranny fluid is supposed to be lifetime but I recently changed it to find the existing fluid was nearly black. Also, since the car was in a dusty climate for most of it's life would that affect the fuel filter needing replacement?
     
  2. mrbigh

    mrbigh Prius Absolutum Dominium

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    It may not be a problem with fuel; probably air intake, recirculating gases, EGR valve,( intake manifold and related)
     
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  3. dorunron

    dorunron Senior Member

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    Could be a weak, but not failed traction battery. I base this on number of miles on vehicle and it's history of climate (hot) during operation (Texas, Florida).
     
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  4. Raytheeagle

    Raytheeagle Senior Member

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    How many miles have you put on it? When you bought the car, did it come with any records of maintenance? What did the spark plugs look like? Correct gap? Intake manifold been off or inspected?
     
  5. bisco

    bisco cookie crumbler

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    have you checked the air filter?
     
  6. ChapmanF

    ChapmanF Senior Member

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    Most of the things (like restricted air filters or fuel filters, injectors, etc.) that would have caused direct engine symptoms in your grandfather's car, in a Prius show up in sensor readings and are compensated for by the computer, so you might not notice any driveability symptoms unless something gets so bad it's outside the range of compensation the computer can effect. Then you just ask the computer what it's compensating for, and that is likely to send you pretty directly to the problem. Just about any OBD-II scantool should be able to show you ignition timing, airflow sensor, oxygen sensor, and long term fuel trim readings. The fuel trim tells you how much the computer had to change its injection pulse width above or below what it 'should' be, seems to be able to go about ±20%. In one thread a few years ago, the car was having problems, the injectors were tested, and turned out to have flow reduced by a bit more than 20%, so the computer's trim was pegged at the maximum and it wasn't quite enough. So a quick valuable way to start is to get those readings from the computer.

    -Chap
     
  7. Kevin_Denver

    Kevin_Denver Active Member

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    Obvious checks are air filter, and 12V battery. If your 12V is going bad your car will be using a lot of energy just to charge it, and in the Prius, this makes it feel sluggish. Otherwise a great tool do more in-depth analysis is to get a Mini Vci cable with Techstream ($15-20 on Amazon), or another OBD scantool. There may be codes occurring that aren't so bad to cause warning lights to show. It can also read sensor values on almost everything in the car, and can tell you how many misfires you've had etc. If it shows misfires or codes for example, then you'd have some evidence and know where to look next.
     
  8. RyanFlorida

    RyanFlorida Member

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    Thanks for the input everyone!
    To answer all of the questions:
    I have cleaned out the EGR piping and air intake a few months ago. I put new spark plugs in when I bought the car in February 2016, I bought the recommended Bosch brand and the package said to not gap them as they are pre-gaped and the gap looked the same as the ones I removed. I have put about 15,000 miles on the car and put in new air filter about 10K miles ago.

    I have been considering the 12V battery to be the problem here as someone suggested. Can this be tested? I know it holds around 11.5V when sitting and over 12V when the car is on. I know this doesn't say much because I had a motorcycle battery that held the charge but a cell must have been broken inside and it didn't have the amperage to start the engine.

    I'll also check out the values on the fuel trim with the scanner to see if I can pick up anything else.
     
  9. Kevin_Denver

    Kevin_Denver Active Member

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    12V battery should read well over 12.4V after sitting overnight, over 12.2 in ACC-ON, 13.8, with car on. 11.5V when sitting points to a battery that needs replacing.
     
  10. RyanFlorida

    RyanFlorida Member

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    So what is done to correct a fuel trim problem?


    Also, any suggestions on a 12V battery?
     
  11. DTKim

    DTKim Member

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    Optima Battery is a good choice for replacement. As for testing your voltage, are you using the on-board diagnostics? That reads woefully low compared to a CALIBRATED multimeter at the battery source. As for calibrated multimeter, I once thought my entire fleet of vehicles had bad batteries due to a multimeter that was reading .2V low (12.3 to 12.5V). I tried my other two multimeters which read the same "normal" voltage as a check and then calibrated the original one to be accurate. Not to say the other two aren't reading a little high, but none of my batteries should've been reading as low as the original one did.
     
  12. ChapmanF

    ChapmanF Senior Member

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    Well, the fuel trim is a clue. If the computer has jacked up the fuel trim, that means it has learned it needs to keep the injectors open longer than expected in order to get the right air/fuel ratio. That would suggest that there is something reducing the normal fuel flow. From there, you've just got old-fashioned gumshoe work ... checking the fuel pump pressure, checking the injector flow rate and spray pattern, etc. Checking for water in the fuel (if the fuel is diluted, the injectors might be totally squirting the right amount of liquid, only not all of it is fuel).

    Or, if you see the computer has learned a fuel trim on the negative side, that might suggest something like a leaky injector that's always letting extra fuel in.

    All of those things are pretty tedious to check, so maybe the greatest value of using a quick scangauge check to look at your fuel trim is that it might come back close to zero, suggesting that you don't have any of those problems, and then you'll look elsewhere and not be tied up in unnecessary tests. :)

    If you have a high-fuel-trim issue that turns out to be injectors, there are services that restore them (using pressurized solvent and new screens and O-rings), I've used Cruzin Performance in Michigan, and they provide you with test results on your injectors before and after. We had a little PriusChat experiment with a few Gen 1s where we sent off the injectors, and in one case the test results confirmed they were the problem (the "before" tests were quite bad), and in another case they passed with flying colors, proving the problem was something else. So the moral there is you can't just assume they're bad; they can be, but can also be near-new in performance even at high mileage.

    I still have the last set of those, back from restoration, but unfortunately I think Gen 3 uses a different injector.

    -Chap
     
  13. RyanFlorida

    RyanFlorida Member

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    I replaced the 12v battery this weekend with an Optima Yellow Top. BTW Amazon best price at $147 w/free 2-day Prime shipping! Instantly I noticed a difference in acceleration and the sluggish feel went away. Another test I performed on the old battery compared to new; with the old battery being used and the car running my OBDII sensor read about 14.2v, when I turned the car off the reading went right down to 12v and trickled slightly further after an hour or so. With the new battery same test the sensor read 14.2v-14.3v when running and at power off it slowly went down to 13v and held there even after an hour. Also, the old battery had a production stamp dated January 2010, so it was probably original to the car.

    Lastly, another problem I have been having with this car is low gas mileage around 40MPG. With the new battery and after about 200 miles driven I am still seeing the 40MPG. Any suggestions for what to check next?

    Thanks all,
    Ryan
     
  14. Raytheeagle

    Raytheeagle Senior Member

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    What is your driving style( most fast highway speeds, in town driving, etc)? Under what driving conditions were those 200 miles logged? Sounds like you have cleaned the egr pipe. How much carbon deposit was in the pipe? PCV valve changed or checked? Throttle body cleaned?
     
  15. RyanFlorida

    RyanFlorida Member

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    I drive the car almost everyday about 50 miles round trip, with 30 miles total on the Turnpike at 80 MPH, the remainder is in town driving between 25 and 50 MPH. I typically don't over accelerate and slowly brake. EGR cleaned and there was a lot of carbon but not enough to block the pipe. PCV valve changed about 10000 miles ago. Upper intake removed and cleaned including the throttle body.

    I took apart all the brakes too and greased slider pins and other components. Although, I only added slider pin grease, I didn't clean out the holes, not sure if that makes a difference.
     
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