Gas Mileage dropped to 28-29 MPG's after new Catalytic Converter and Shield installed. WHY?

Discussion in 'Prius c Fuel Economy' started by Owner of "Little Green", Aug 16, 2022.

  1. Owner of "Little Green"

    Owner of "Little Green" Junior Member

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    I had my Catalytic Converter stolen in June and paid to have a shield put over the new CAT. Immediately after that my MPG's dropped to 28 to 29 MPG's. What happened?
     
    #1 Owner of "Little Green", Aug 16, 2022
    Last edited: Aug 16, 2022
  2. rjdriver

    rjdriver Active Member

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    Did you have the Cat replaced at a Toyota dealer?
     
  3. priusCpilot

    priusCpilot Active Member

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    Do you have a Prius C or a Prius 2006 Gen 2?
     
  4. audiodave

    audiodave Active Member

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    Is that a calculated tank?
    Posted via the PriusChat mobile app.
     
  5. bisco

    bisco cookie crumbler

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    is it a catshield?
     
  6. Redline96

    Redline96 New Member

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    There's a few variables I can think of. If the exhaust header and the catalytic converter are separate then that could do it; Toyota (/OE) design has the converter and the exhaust manifold combined. Either one, or both, of the oxygen sensors could've been damaged with the removal. It's possible that the new installer did damaged O2 sensors, but highly improbable. An exhaust leak could cause it (any new smells)? Do you have a check engine light on or a heat coming into the cabin from the floor? If an aftermarket converter was put in, it might be too restrictive for the Prius C's design parameters. Did you get a used converter? Used ones could be clogged and cause the engine to work harder.
     
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