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Thread: Failed smog due to a fried ecu

  1. #1

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    Angry Failed smog due to a fried ecu

    Recently failed smog. I had my engine and heads rebuilt at 229000 miles. I had replaced oxygen sensor, TPS sensor, spark plugs, wires cap and rotor, catalytic converter, ignition coil, engine temp sensor, cracked exhaust manifold, radiator hoses thermostat. my mileage now is about 257000 miles.my truck had gradually started too run very rich, MPGS were very poor. @10 mpg. when I had taken it smog. my base timing was 10deg.BTDC anyways failed. so I took it to a mechanic which was recommended by a buddy of mine. after being in the shop he check top to bottom for the problem, turns out the computer was fried. after replacing the ECU it still failed. IM thinking WTF! my mechanic recommended driving it around a couple hundred miles to burn off any crap stuffed in the catalytic converter. before I smog it again

  2. #2

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    I forgot to mention that I replaced the fuel injectors, the fuel Pressure regulator and fuel filter

  3. #3

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    I would be surprised it would run at all if the ecu was"fried".
    1990 MM 4x4 3.0
    1991 MM 4x4 3.0 Diamonte
    1994 MM 2wd (work in progress)

  4. #4



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    I agree, the ecu determines mixtures and well, just about everything else that is smog related though. You poor guys living in California, get the hell out of that state. It won't be long before you have to smog your bicycles,


    Burn off stuff in the catalyst? Oh he must mean wait till it burns the truck down maybe.

  5. #5

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    Post the results of the 5 gas analysis on the printout you got when it failed (15/25 mph test). CO, CO2, O2, HC and NOx.

    10 degrees is advanced on the 2.4 right? I thought spec was 5 degrees.

    -noahwins, smog inspector

  6. #6

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    took the mm on Friday morning to a smog check n repair shop . dude charged me 80 for the diagnostics turn out the base timing was way off 36deg. BTDC distributor was off by one tooth paid 125total that included the smog cert. I was so glad it had passed smog.as for the other mechanic I had initially took my truck to I will never take my truck to him again...

  7. #7

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    That would explain the bad gas mileage the distriutor being off,

  8. #8

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    yeah, was almost gonna give up on the MM. it was getting 10mpg .I drove it like that for months. I was too cheap to take it to a shop, yet I had no problem shooting from the hip and replacing shit like a tps that set me back 200 $ thinking it wouldfix my mpg's

  9. #9

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    What's your gas mileage now that you have everything fixed

  10. #10

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    much better but ill get an accurate # on Monday. Ill fill her up and see, I have like a 300 mile commute. all hwy miles

  11. #11

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    Good to hear a happy ending! I sure hope that's not a daily commute.
    1990 MM 4x4 3.0
    1991 MM 4x4 3.0 Diamonte
    1994 MM 2wd (work in progress)

  12. #12

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    I figure out my mpg s today. 24 miles per gallon. what do you guys think? should I be getting better?

  13. #13

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    How fast are you going on average? I hear a lot of guys getting close to 30 mpg but I would bet that's at 65 or under. Curious to hear what most MM's get.
    1990 MM 4x4 3.0
    1991 MM 4x4 3.0 Diamonte
    1994 MM 2wd (work in progress)

  14. #14

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    25-27 at 65 or so.

  15. #15

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    average speed is 70/75

  16. #16



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    Try running 55 or 60 and see how high it goes. But thats good. I only got about 15
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  17. #17

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    15! You must be doing about 95!
    1990 MM 4x4 3.0
    1991 MM 4x4 3.0 Diamonte
    1994 MM 2wd (work in progress)

  18. #18


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    I got 20.6 last full up.
    1989 Mitsubishi mightymax; 1990 4g63 6 bolt swap: malhe 9.0 pistons, eagle h beam rods, acl race bearings, rebuilt head, evo 3 16g, aem afpr, Maft, 3" gm maf blow through, walbro 255 fuel pump, hks ssq bov, fmic, coil over plug, FIC 750 injectors, dsmlink, apexi avcr, AEM eugo, s90 throttlebody, JMF FIAC block off plate. LT1 T56 in the works.
    Why a mightymax? Why not? 18 psi FTW.

  19. #19

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    I get around 23-26. So sounds about right.

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