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Thread: 7MGE Fuel Economy

  1. #1
    Forum Member 1st year Apprentice
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    Default 7MGE Fuel Economy

    I have a '91 Grande and rebuilt the engine with bores, pistons, rings, seals and bearing. With Andrew_MX83 we took 1mm from block/head and the car now runs like a dream with higher compression. But it uses a lot of fuel, around 18l/100kms around town driven carefully.

    Started cold after 400m down he road the engine lamp comes on and stays on until you shut it down, then restart. It runs fine and the plugs look very clean. I have replaced the oxygen sensor, but can't figure out why it's so uneconomical. Engine and trans use fresh oil, filters are new, brakes are not binding. I had expected it would be around 11l/100kms but it's 60% higher than that.

    I'm thinking it might be an ECU issue. It runs beautifully with terrific torque and power, you would think it was a turbine!

    Any ideas? Any tests to uncover this issue? The fuel usage is making me broke........

    Hugh

  2. #2
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    Default Re: 7MGE Fuel Economy

    have you got a modified fuel system? i cant think, if its so called burning this fuel? without having rich plugs, and it seems to be running right, where can it be going??? is there any leaking (fuel)
    what if you let it idle for about 30mins, then check the plugs?just to see what its doing at idle, im asking blind questions, only due to its running right???

  3. #3
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    Default Re: 7MGE Fuel Economy

    Hi X,
    Thanks for answering!
    No, standard fuel system, no changes. Can't smell fuel except from the tail pipe, so I'm assuming it's an ECU issue but really can't figure it out, ECUs are beyond me.
    I will will try the idle for 30 mins and check the plugs again. But it runs so well it gives me the feeling it's in limp home mode.
    HD

  4. #4
    Junior Member Backyard Mechanic jondee86's Avatar
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    Default Re: 7MGE Fuel Economy

    Possible to check for fault codes ?

    If MAP sensored engine check engine vaccum at idle.

    Thermostat working so engine gets up to normal operating temp ?

    Cheers... jondee86

  5. #5
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    Default Re: 7MGE Fuel Economy

    Yes, runs at correct temp, new thermostat.
    How do I access fault codes? Thanks in advance,

    HD

  6. #6
    Junior Member Backyard Mechanic jondee86's Avatar
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    Default Re: 7MGE Fuel Economy

    Pretty sure this thread will cover it...
    https://www.troublecodes.net/toyota/...ra-3-0l-turbo/

    Jumpering the two pins in the diagnostic box is standard procedure for old Toyotas. Here is one with the lid opened... it will be in the engine bay somewhere



    I would expect the 7MGE codes to be the same as the 7MGTE codes. but might pay to check.

    Cheers... jondee86

  7. #7
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    Default Re: 7MGE Fuel Economy

    Thank you JD, I will try this tomorrow!

    HD

  8. #8
    Toymods Board Member Chief Engine Builder Hiro's Avatar
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    Default Re: 7MGE Fuel Economy

    Quote Originally Posted by jondee86 View Post
    Pretty sure this thread will cover it...
    https://www.troublecodes.net/toyota/...ra-3-0l-turbo/

    Jumpering the two pins in the diagnostic box is standard procedure for old Toyotas. Here is one with the lid opened... it will be in the engine bay somewhere



    I would expect the 7MGE codes to be the same as the 7MGTE codes. but might pay to check.

    Cheers... jondee86
    The pins circled in that picture are wrong for diagnostics TE1 (the pin above VF1) and E1 are the ones you bridge for diagnostics via the CEL/MIL.
    AE102 - Charlene the Old Faithful, Reborn
    JZZ30 - Lexi the Spacecruiser, 1JZGTE>>3SGE. 200rwkw, hunting Skylines and n00bs in SS Commodores
    ST162 - Charlie the non-ghey Celica, 3SGE>>4AGE. GOOOOOOOONE
    AE82 - Rosie the Bitsa from Hell, 70.8kw atw. Has been converted into garage space and money at last
    KE55 - Billie the Beast, sadly missed

  9. #9
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    Default Re: 7MGE Fuel Economy

    Thanks Hiro, much appreciated.

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