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After running low on fuel, CEL! Cleaned MAP sensor, now bad mpg.

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by a11m1ghty, Feb 6, 2014.

  1. a11m1ghty

    a11m1ghty New Member

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    Driving on teh interstate to a Kroger to fuel up, and I was running low on gas. I was speeding in fact. 80+ mph. My check engine light came on. My diagnostics pointed to the Lean bank 1. I cleaned my MAP sensor and reset my CEL. Since then, no CEL but am getting horrible mpg. Previous MPG 53, current MPG 42.

    Do you think my MAP is damaged but not throwing a code or my catalytic converter get damaged/plugged? Driving on battery from a complete stop to 24MPG it's normal, when the engine kicks in, it goes down to the teens. Changed oil (Synthetic oil) 1 month ago.
     
    #1 a11m1ghty, Feb 6, 2014
  2. JC91006

    JC91006 Senior Member

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    How many miles are on your car? It could be a bad O2 sensor that hasn't re-triggered the CEL. But 43mpg isn't exactly bad, it's actually the mileage I normally see on mine. I often see mileage in the teens when I'm accelerating from a stop.
     
    #2 JC91006, Feb 6, 2014
  3. a11m1ghty

    a11m1ghty New Member

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    188K. I was averaging mid 20's when accelerating from a stop. A full tank used to net 450's - 490's (depending on driving habit/style) miles. Now I'd be lucky to hit 375. Horrible. I'm currently at 1 bar of fuel left and have driven 358 miles.
     
    #3 a11m1ghty, Feb 7, 2014
  4. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Exactly what was the DTC that was logged?

    I think that you should consider the possibility that the air/fuel ratio sensor may be worn and needs to be replaced. That is what provides feedback to the engine ECU regarding air/fuel mixture and if it is getting marginal, your fuel economy certainly will be impaired.

    The mass air flow sensor also is vital to the proper functioning of the engine ECU since that measures the metered air flow into the throttle body. I hope you used only the correct MAF sensor cleaner and not throttle body cleaner on that part.
     
    #4 Patrick Wong, Feb 7, 2014
  5. a11m1ghty

    a11m1ghty New Member

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    CEL code " Lean Bank 1". Been a while so I don't know the numerical code.

    However, I did use brake cleaner to clean the MAP sensor. The clerk at auto zone told me it was ok to use.
    If I had any auto R/C motor cleaner (For small electrical engines), I would've used it instead.

    I too was leaning towards replacing the MAP sensor, but just didn't want start throwing parts at it. Logical move, I'll swap it out today and report back . I need to get my close to 500 miles to the tank back so I can brag to co-workers again. LOL!
     
    #5 a11m1ghty, Feb 7, 2014
  6. Patrick Wong

    Patrick Wong DIY Enthusiast

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    I don't think that brake cleaner is suitable because it is very harsh and can damage plastic parts. You might try using mass air flow sensor cleaner first, before you replace the part.

    By the way, the Prius engine does not use a MAP (manifold absolute pressure) sensor. Rather it uses a MAF (mass air flow) sensor.
     
    #6 Patrick Wong, Feb 7, 2014
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  7. Edyb

    Edyb New Member

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    Actually, Gen. 3 prius does have a MAP sensor that is located on the intake manifold underneath the air filter assembly and also have a MAF sensor before the air filter
     
    #7 Edyb, Apr 19, 2019
  8. dolj

    dolj Senior Member

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    Actually, this is the Gen 2 forum and we are discussing a Gen 2 problem, so it really doesn't matter what goes on in a Gen 3.
     
    #8 dolj, Apr 21, 2019
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  9. ChapmanF

    ChapmanF Senior Member

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    I suppose Edyb's point might have been that Patrick's "the Prius engine does not use a MAP" might better have been "the 1NZ engine" (the one used in Gen 1, Gen 2, and c). Just in case somebody skimming threads would see this one in the Gen 2 forum and end up thinking it applied to every Prius engine.
     
    #9 ChapmanF, Apr 21, 2019
    m.wynn likes this.
  10. Edyb

    Edyb New Member

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    I stand corrected, I have been reading many posts trying to figure out my problem and somehow I ended up reading this gen 2 tread, I'm still trying to figure out my issue, as soon as I figure it out I will talk about it, it could help someone down the road
     
    #10 Edyb, Apr 23, 2019
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