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Smog test fail - Questions

Discussion in 'The Lounge' started by mtn. burb, Aug 11, 2004.

  1. mtn. burb

    mtn. burb 1/2 ton status

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    This is on the 93 burb' mommy-mobile. I installed a new stock 350 GM crate motor in it about 6 months ago. She took it to the smog test station spent 42 bucks and it failed. The guy said it showed a code 44 failure. This indicates lean exhaust temp. The oxygen sensors have been replaced, could it be a bad oxygen sensor or what other thing would cause a lean exhaust temp ?
    Thanks
     
  2. Goober

    Goober 1/2 ton status

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    How can a temperature be lean? /forums/images/graemlins/confused.gif "Lean exhaust temp" sounds pretty strange.

    If it is running too lean then that will cause the temp to go up in the exhaust. Mixture is partly controlled by the O2 sensor, you may want to have it checked.
     
  3. K5MONSTERCHEV

    K5MONSTERCHEV 1/2 ton status

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    You're right ya Goober!

    Lean exhaust temp, HMM, that is fishy, or the guy didnt know exactly what the problem was. If you replaced, the o2 sensors, and there not GM sensors, then they could be bad, even though there new.

    Code 44 is o2 sensor lean, so either the cr is running lean all the time or the o2 is not switching. If its runing lean then the o2 and HC were high correct?

    Either way, check the o2 sensor. See if its putting out a signal (backprobe), it should be switching between rich lean, 200 and 800 mV, if not then replace sensor, if it is check it it the computer harness, if it is you have to see if the engines runninglean or not with the smog machine. If its lean theres a vaccuum leak, or a restriction on the fuel side.

    Hmm I think thats all.
     
  4. ntsqd

    ntsqd 1/2 ton status

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    Who'd you take it to?
    I take all my rigs to Smoggies on Market St. here in Vta.
     
  5. jarheadk5

    jarheadk5 1/2 ton status

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    Along with the vacuum lines, check your TBI-to-intake manifold gasket. Any air leaks past the butterflies are called "false air" because it wasn't measured by the MAP sensor. If the computer doesn't know about the extra air getting into the motor, it can't compensate by adding fuel to richen the mixture.
    My cousin had the same problem when he had his '87 K5 inspected - tech failed him for a code 44. We checked vac. lines, all good. We sprayed a bit of carb cleaner around the TBI base, and when the motor revved a bit, we knew we found the air leak.
     
  6. 88Silverado

    88Silverado 1/2 ton status

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    Try changing the fuel filter. Mine was setting a Code-44 (Lean Exhaust) when I would get about 45-50MPH. It was also pretty doggish. My fuel filter was plugged. It wasnt getting enough fuel at higher RPMs thus going into Lean condition. Filter was only $6 or so.. /forums/images/graemlins/tongue.gif
     
  7. mtn. burb

    mtn. burb 1/2 ton status

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    Thank you for your replies. You're all correct: not temp. /forums/images/graemlins/doah.gif code 44 is lean exhaust condition. I'll work it out. Thank you again.
     

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