rich prius map sensor reads but engine hasn't got one?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by sergbot, Nov 25, 2021.

  1. sergbot

    sergbot New Member

    Joined:
    Jan 19, 2021
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    Location:
    Hawaii
    Vehicle:
    2009 Prius
    Model:
    N/A
    So i've been trying to tackle my rich running prius for over a year now.
    I replaced the spark plugs, coil packs, fuel injectors, upstream o2 sensor. I don't have a downstream o2 sensor because it was cut off in a theft. I saw that the prius was reading the manifold pressure sensor as existing and it was slow to change the reading, and it was always 81 kpa, and it was the same if the engine was on or not. Sometimes it would occasionally read 104, so i decided it was faulty then discovered it doesn't exist.

    At idle i get about -25% long term fuel trim. Going up hill at 60 mph, i still get -7% long term fuel trim, spiking up more negative whenever I let off the gas. So the car is running super rich. I can also smell my exhaust when I start the car.

    When the engine idles for the first time in the day, it runs at -10 timing, to warm up i guess? and during this -10 timing, i get misfires and misfire codes. When timing is normal 5-20, then i don't get misfires.

    As far as I can tell the maf sensor works fine. 0.09 at engine off. 2+ grams at idle. And 45+ grams under heavy load.

    Yeah not sure how to proceed. Could be over pressured fuel pump. Could be the maf sensor?
    Could be engine issue?
    Not sure how to crank the engine for a cyl pressure test on a hybrid lol
     
  2. nancytheprius

    nancytheprius Member

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    Location:
    iowa
    Vehicle:
    2006 Prius
    Model:
    II
    have you tried cleaning the maf sensor yet? it’s really simple and id recommend doing it!
     
  3. sergbot

    sergbot New Member

    Joined:
    Jan 19, 2021
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    Location:
    Hawaii
    Vehicle:
    2009 Prius
    Model:
    N/A
    i checked it today and decided to buy a replacement that's in the mail. It was a weird experience. At first, when it was working under load. it would do 1500 rpms charging and was doing 6 grams. Trying to rev it to 2600 got 8 grams. Then when it wasnt charging i was getting 3 grams at 1300 rpms, and 6 grams at 2600. The tps was always 17, and it would go to 20+ when i revved it. However I noticed a lot of lag in the reading, and I noticed that when the revs were coming down, and the engine was turning off, it would randomly spike to 3 grams in the middle of winding down. A new maf sensor is only 20 bucks on amazon, 100 bucks locally. Ill try to clean it tomorrow and see if that effects my fuel economy, but i do remember cleaning it before. I also got a voltage regulator and also a 8 amp pulse width modulator, gonna see if i can hook it up in the fuse box to turn down the juice on the fuel pump and see if that has any effect.
     
  4. edthefox5

    edthefox5 Senior Member

    Joined:
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    Location:
    Clearwater, Florida
    Vehicle:
    2007 Prius
    Model:
    Two
    I don’t have a downstream sensor as it was cut off in a theft.
     
    SFO likes this.
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