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Cleaned/removed TB and MAF now hiss?

02suburbanZ71

By 02suburbanZ71
in Ask A GM Technician

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02suburbanZ71 Senior Enthusiast

02suburbanZ71

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At work a coworker and i removed my drive by cable TB, MAF, and changed the oil. We had to remove the coolant lines and vacuum line from the TB to remove the TB for cleaning (it was very dirty) now at idle i have a small hiss noise i can hear from inside. It sounds like a vacuum noise. Not sure any ideas on the culprit? All the hoses seemed very snug when i replaced and no CEL. Runs perfect

02suburbanZ71 Senior Enthusiast

02suburbanZ71

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Also we disconnected the battery for the whole process and i only drove it home which is 6 miles

02suburbanZ71 Senior Enthusiast

02suburbanZ71

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Did not replace the gasket. Where should i aim the propane tank. Right around the TB? I have one at work i'll have to do it then

Doug_Scott Senior Enthusiast

Doug_Scott

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put a rubber hose on the propane tank and feed the rubber hose all around the area you worked in. Don't be surprised to find a cracked or broken hard plastic vacuum line, or something stupid like misaligned air box and/or air box host that goes from box to throttle body. Sometimes a vacuum leak is so small it will not set a code. Other times they can be so big that it confuses the MAF sensor. The engine will get more air than the sensor measured. Under heavy throttle vacuum leaks actually slow down due to less vacuum at heavy throttle.

02suburbanZ71 Senior Enthusiast

02suburbanZ71

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Heres an update. It seems to idle high, when im in reverse or drive it drives with my foot off the gas. It also does not seem to have as much response. I have a blackbear tune and it does not drive like it did before. I think im gonna take it to the dealer. Do you think they can fix it without removing my tune?

48548 Enthusiast

48548

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Idle air control valve messed up? It is in the throttle body. There is a way to reset it. I would check it yourself before paying someone.

02suburbanZ71 Senior Enthusiast

02suburbanZ71

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Could resetting it fix my hesitation and lack of power? My k&n intake always made a nice deep noise- never had an intake leak now it doesn't make The same growling noise

48548 Enthusiast

48548

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It opens to let air in with the throttle blade is closed. Not sure what it would do. It sounds like you have a vacuum leak, because that makes a faster idle I have seen.

02suburbanZ71 Senior Enthusiast

02suburbanZ71

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It idles high, like 900 RPMS, and it hesitates a bit like it did before my blackbear tune. It feels stock now except it still shifts hard. BTW i have DBC not wire i think that has something to do with it

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