failed smog test again. the HC is still high @15MPH
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Northstar Engines and System Technical Discussion Discussion, failed smog test again. the HC is still high @15MPH in Cadillac Engine Technical Discussion; I replaced spark plugs, FPR, oil, airfilter and ran about 20 minutes before the 2nd test but the results are ...
  1. #1
    31415926's Avatar
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    failed smog test again. the HC is still high @15MPH

    I replaced spark plugs, FPR, oil, airfilter and ran about 20 minutes before the 2nd test but the results are same: high HC @ 15mph.
    Any ideas?
    Thanks!


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    ewill3rd is offline Cadillac Technician
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    Re: failed smog test again. the HC is still high @15MPH

    You really need to run some fuel system tests.
    Your fuel pressure could be too high or you could have a leaking injector.
    I have seen a few of both.

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    Re: failed smog test again. the HC is still high @15MPH

    Quote Originally Posted by ewill3rd View Post
    You really need to run some fuel system tests.
    Your fuel pressure could be too high or you could have a leaking injector.
    I have seen a few of both.
    If it's a fuel pressure thing, could you tell me why it passed HC@ 25mph?

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    Re: failed smog test again. the HC is still high @15MPH

    The slightly increased (engine) speed results in higher combustion chamber temperatures and thus lowers HC. Start looking at fuel pressure and injector leaks. High HC is analogous to a stuck choke in a carbureted engine. (You'll notice that one more digit in your 25 mph HC and it would also have failed. You're running rich.)

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    ewill3rd is offline Cadillac Technician
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    Re: failed smog test again. the HC is still high @15MPH

    sub is right, the higher engine load will use up more HC, the throttle plate is open more so you have more O2 for combustion.
    At any rate, it is a place to start.

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    Re: failed smog test again. the HC is still high @15MPH

    Quote Originally Posted by submariner409 View Post
    The slightly increased (engine) speed results in higher combustion chamber temperatures and thus lowers HC. Start looking at fuel pressure and injector leaks. High HC is analogous to a stuck choke in a carbureted engine. (You'll notice that one more digit in your 25 mph HC and it would also have failed. You're running rich.)
    Leaky FPR?

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    ewill3rd is offline Cadillac Technician
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    Re: failed smog test again. the HC is still high @15MPH

    He looked for that in another thread I am pretty sure.

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