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Mileage issues with new tires/roof rack possible gas leak?

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by scottwg, Sep 8, 2015.

  1. scottwg

    scottwg Junior Member

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    This could have easily gone in the mileage thread, but there are other issues that I am dealing with too. Hi all. First post. I have been using PriusChat for years, but I have always gotten the answers I needed without having to sign up. This is complicated and goes in a lot of directions. Briefly, I got new tires. Not the ones I should have and I knew it. I do not expect to have the car for more than a year or two more so I did not want to spend the money on the correct tires. Probably a mistake but oh well now. I have over 211K on the car. At the same time I got the tires I put a Yakima rack on the car. And for discussion's sake, I installed a new Dorman hybrid battery myself about a year ago. And there is a new 12v too. I was surprised that after installing the new hybrid battery I did not really get any better mileage. I admit I have a heavy foot. I would get at best 44-46 mpg. But my wife also has a newer 2011 and I can get 48-50 in hers. Now, with all the new stuff and tires, I am lucky to get 41 if I am really careful. Now, after all that explaining, this is my question: I found a fuel leak a year ago that was almost impossible to find. I could smell the gas. It was a broken fuel line near a clip on top of the engine. I swear I might be smelling gas again. Are there well known points where there have been fuel leaks that I can check? My mechanic did not even find the first one after a thorough check. I was with him and helped. I was lucky to find it myself after checking further. I am also having acceleration issues when I first start off. Intermittent pauses in acceleration that go away after the first few minutes and can even cause me to have trouble pulling out in traffic when I floor it. But I can talk about that one later. Just thought I would bring it up now just in case it sounds related.
     
  2. Mendel Leisk

    Mendel Leisk Senior Member

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    As you describe, it sounds like a lotta things working in concert to pull your mpg down. What specifically are the new tires, btw.
     
  3. scottwg

    scottwg Junior Member

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    Kumho 185/65 40K mileage. Rated for 44 psi, but I have them up at 51 right now.
     
  4. bisco

    bisco cookie crumbler

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    welcome! i doubt you're going to get much improvement on a 10 year old car with 200,000 miles. enjoy it for what it is. all the best!(y)
     
  5. scottwg

    scottwg Junior Member

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    Yeah, you're probably right. Just thought I would try and find something that could be fixed if possible.
     
  6. Mendel Leisk

    Mendel Leisk Senior Member

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    Well, except maybe fix the gas leak? :whistle:
     
  7. scottwg

    scottwg Junior Member

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    Yeah, that is really my main concern. I was hoping this might be something that has happened to others and might know some common places where this has happened before. The Toyota dealership was not very helpful. Also, what is going on with that intermittent power problem? Can it be pinpointed to an electrical device? Maybe this question would be better in a new post, or if someone is familiar with this problem, point me to a thread where it has been previously discussed.
     
  8. AffordableCarCareNC

    AffordableCarCareNC New Member

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    It does sound like a combination of problems. I am a Toyota MDT and owner of Affordable Car Care in Raleigh, NC. Higher rolling resistance tires will very much hinder fuel mileage on a Prius. The rack probably does not help.

    As far as fuel leak/smell- If you smell it when ac is set to outside air with the windows up then most likely place is the fuel line that connects to the rubber line going to the engine. It has a Teflon coating that often pills back especially after a EFI service. If you see fuel around it I would consider disconnecting it and checking for damage to the coating. You can take a razor blade and cut the damaged coating back but do not cut up to the bump on the line. That is where it seals and will likely leak if that is cut. If it still leaks the steel line will need to be replaced.

    As far as the acceleration problem- It may be because of the fuel leak but it may also be a leaf or other debris in the MAF partially blocking the Mass Air Flow sensor. This commonly occurs after checking the air filter. It sometimes causes a MIL but not always depending on how bad the blockage.
     
  9. scottwg

    scottwg Junior Member

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    Wow, great advice! I will be checking this today. Thanks. I was told the other day by someone who had an older Prius to check/change the spark plugs. I guess I am just not used to doing that on these newer cars. But I wanted to get someone's opinion on that. Easy enough to do, but do they really get fouled up on such a lightly used engine?
     
  10. szgabor

    szgabor Active Member

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    Looks like you compare a GenII to a Gen III ??? Gen 3 has about 10-12% efficency I was very pleased to see that when I got my 2010 !!! after the Gen II ... (missed the backup camera and few other things but gained 4-5 mpg on the same route...
     
  11. Mendel Leisk

    Mendel Leisk Senior Member

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    Second Gen I understand are relatively easy to access plugs. I've dug down to ours (3rd gen) a couple of times (I know, borders on an illness...), and there's an insane amount of disassembly required. Anyway: even if you don't change the plugs (they tend to be super long life), it's worthwhile, just to ensure against them getting too hard to remove, and to have a look at them.

    Not sure what size 2nd gen plugs are, 3rd gen requires oddball 9/16" socket, so having a variety of spark plug socket sizes on hand would be worthwhile. And at least a 6" ratchet wrench extension. You should have a decent low range torque wrench. I ended up using a VERY sparing amount of anti-seize compound on the threads, and torqued to 13 lb/ft.
     
  12. scottwg

    scottwg Junior Member

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    Excellent. Thanks again.
     
  13. fuzzy1

    fuzzy1 Senior Member

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    The roof rack portion of mpg loss should be easy to check. Just temporarily take the rack off.
     
  14. Mendel Leisk

    Mendel Leisk Senior Member

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    And none of the Kumho's I look up on TireRack say LRR. Next time.
     
  15. scottwg

    scottwg Junior Member

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    Ha! True fuzzy1. LRR tires? I assume that is the Silicon content? Or pressure rating maybe? At any rate, you're right. Next time.
     
  16. Mendel Leisk

    Mendel Leisk Senior Member

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    Besides the LRR badge, you need to read up. There's a wide range within LRR, some are marginal.
     
  17. scottwg

    scottwg Junior Member

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    Yeah, I will check it out. I am kind of scared to. I am sure it will get me mad at myself. But I will only have the car for a little while longer. I just want to try and tackle the possible fuel leak. If nothing else, before I sell it to someone. I checked inside the fuel filter. I was surprised to see some carbon buildup on the air intake. When I opened the carb all the way, there was a little oil visible inside. If that is the case, I am sure the plugs could be changed out. I am looking into that now. By the way Mendel made it sound, it might not be too fun. But worth it.
     
  18. Mendel Leisk

    Mendel Leisk Senior Member

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    When I cleaned our 3rd gen throttle body (around 50000 km) I saw oil too. Couldn't quite understand what I was looking at first, it was so improbable. This was down beyond the valve. Looked like a lake! Due to PCV valve??
     
  19. scottwg

    scottwg Junior Member

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    Luckily there is not that much oil. I would certainly be concerned if there was that much. It is just a heavy film of oil. But more than I would think would be in an engine like that.