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Thread: Installed headers wont run in CL

  1. #1
    Lifetime Member minytrker's Avatar
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    Default Installed headers wont run in CL

    I just installed headers on a 04 silverado. Before the install the check engine light was on for the O2's being bad. I installed the headers but the O2's had to be ordered so I just put the old ones back in. Drove the truck 60 miles that night then the next day it wouldnt run without bucking and getting misfire codes and flagging the o2's. I put in 2 new O2's and cleared the pcm and it still does it.
    So far I have checked for burnt wires, nothing even close to the headers. I checked the O2 voltage when driving, checked the plugs. With these headers there are no extensions, and its impossible to plug them into the wrong plug. Im lost the truck is undriviable in CL, can only be driven in OL.

    Any ideas on what to check?

  2. #2
    Lifetime Member Doc's Avatar
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    Is it both banks or just one?

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  3. #3
    Joe (Moderator) joecar's Avatar
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    It runs in OL but not CL... plugs/wires must be ok.

    What were the DTC's before and after the header install...?

    Can you post a log showing HO2SV11 and HO2SV21 (voltage from front sensors on both banks).

    Check for airleaks upstream of the NBO2 sensors, or downstream for about 1 foot.

  4. #4
    Lifetime Member minytrker's Avatar
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    Quote Originally Posted by Doc
    Is it both banks or just one?
    Both. When I bought the truck they were both flagged but I could clear the DTC's and drive it for about a week before they would come back on. It also didnt run bad when the O2's flagged. Now after the headers when the O2's are flagged the truck will barely run.

  5. #5
    Lifetime Member minytrker's Avatar
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    Quote Originally Posted by joecar
    It runs in OL but not CL... plugs/wires must be ok.

    What were the DTC's before and after the header install...?

    Can you post a log showing HO2SV11 and HO2SV21 (voltage from front sensors on both banks).

    Check for airleaks upstream of the NBO2 sensors, or downstream for about 1 foot.
    I will have to look again but it for O2 heater for O2 Bank 1 sensor 1 and banks 2 sensor 2.
    There are no leaks at all.

  6. #6
    Lifetime Member Bruce Melton's Avatar
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    As you know when the 02s are unhappy it will not switch to CL.
    There are zillions of theories on keeping the 02s active, but I find they run much better with - trims at and near idle.

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  7. #7
    Lifetime Member minytrker's Avatar
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    Quote Originally Posted by Bruce Melton
    As you know when the 02s are unhappy it will not switch to CL.
    There are zillions of theories on keeping the 02s active, but I find they run much better with - trims at and near idle.

    It switches to cl it just wont run in CL. If you try to drive it it will start cutting out and throw engine missfire code.

  8. #8
    Lifetime Member minytrker's Avatar
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    I still have not found the cause but I did find out that I have a small exhaust leak right in front of both O2's where the headers meets the tail pipe. Both sides are barley leaking. Would that be enough to make it go crazy in CL? Also even with new O2's I keep getting O2 heater sensor 1 bank 1 and sensor 2 bank 1 faults.

  9. #9
    Lifetime Member Biggsy's Avatar
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    Check your earths.
    Dave.

  10. #10
    Lifetime Member johnv's Avatar
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    Do a cylinder balance check, you may have a loose or damaged spark plug lead !

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