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  1. #1

    Default Maybe a dumb question

    But can my knock sensors being bad rob me of fuel efficiency or make my O2 sensors read faults?

    Dont want to have to dig into the truck too much as that stuff costs money. But so does gas.



    If at first you don't succeed, chances are, you are using too small of a cheater bar

    Current:
    1999 GMC Sierra SLT Z71 | 5.3 Vortec | Spectre Cold Air Intake | TransDapt TBS | Hypertech 30005 Tune | 2005 Chevy Tails | Denali headlights | AWS Bug Shield | 265/75/16 Mastercraft Courser A/T | "Ghetto" painted tailgate | Boss HD Speakers | 2005 Overhead Console | Dual Thrush Turbo Mufflers
    Future:
    Bigger Amp Alternator | Electric Fans | Oil/Trans Fluid cooler | Re-done exhaust | Paint | Interior Restoration/upgrade with newer model stuff | Window Visors (In channel) | Tint | Low-Profile Tool Box | LEDs throughout stock cab locations | And whatever is spurr of the moment
    US Navy Sailor :sign0011:

  2. #2

    Default

    Yes. The knock sensors are an important part of the ignition system, and their proper functioning helps the computer to adjust spark timing, so that a more complete burn of the fuel can happen. With bad knock sensors, you could not be completely burning the fuel, which can damage the O2 sensors, and then cause them to fault, making the gas mileage even worse.

  3. #3

    Default

    Exactly the news I was looking for... New project for the week. @Sierraowner5.3?



    If at first you don't succeed, chances are, you are using too small of a cheater bar

    Current:
    1999 GMC Sierra SLT Z71 | 5.3 Vortec | Spectre Cold Air Intake | TransDapt TBS | Hypertech 30005 Tune | 2005 Chevy Tails | Denali headlights | AWS Bug Shield | 265/75/16 Mastercraft Courser A/T | "Ghetto" painted tailgate | Boss HD Speakers | 2005 Overhead Console | Dual Thrush Turbo Mufflers
    Future:
    Bigger Amp Alternator | Electric Fans | Oil/Trans Fluid cooler | Re-done exhaust | Paint | Interior Restoration/upgrade with newer model stuff | Window Visors (In channel) | Tint | Low-Profile Tool Box | LEDs throughout stock cab locations | And whatever is spurr of the moment
    US Navy Sailor :sign0011:

  4. #4

    Default

    Dumb question follow-up: how long do knock sensors usually last or what is a good interval to change them?
    Clint (TX) 2001 Silverado LS 4.8L auto 2wd ECSB [GARAGE]
    Gasoline or gunpowder: If you ain't burning one, you ain't having fun!
    NRA Endowment Member 5 24 48 88 - Hendrick Motorsports FTW!

  5. #5

    Default

    I always thought when they throw codes. Water likes to get under the intake. Come to think of it I gotta change the head gaskets anyway so...



    If at first you don't succeed, chances are, you are using too small of a cheater bar

    Current:
    1999 GMC Sierra SLT Z71 | 5.3 Vortec | Spectre Cold Air Intake | TransDapt TBS | Hypertech 30005 Tune | 2005 Chevy Tails | Denali headlights | AWS Bug Shield | 265/75/16 Mastercraft Courser A/T | "Ghetto" painted tailgate | Boss HD Speakers | 2005 Overhead Console | Dual Thrush Turbo Mufflers
    Future:
    Bigger Amp Alternator | Electric Fans | Oil/Trans Fluid cooler | Re-done exhaust | Paint | Interior Restoration/upgrade with newer model stuff | Window Visors (In channel) | Tint | Low-Profile Tool Box | LEDs throughout stock cab locations | And whatever is spurr of the moment
    US Navy Sailor :sign0011:

  6. #6

    Default

    im more or less one armed right now, but i will help with what i can.

    Alex


    2011 GMC Sierra SLE 5.3 Z71 4X4 Stealth Gray Metallic / 2004 Chevy Impala LS 3.8 Cappuccino

    Tow mirrors - Diablew Tuned - Flowmaster Regular 40 - Ready Lift 2.5' lift - BFG LT A/T K/Os - Carr Light Wing - TruckLite LED lights - Optima Red Top - 50% Front Window Tint - Line-X bedliner - Airaid MIT - Tekonsha P2 - ARS Billet Grill - Fia custom fit seat covers

  7. #7

    Default

    Mine went about two years ago, but it was completely my fault. I was out of town for work for about two weeks. Knowing when I got back I had to change the oil and stuff. So when I returned and started to add the oil I noticed a nice mouse nest under the intake. So I took my pressure washer and sprayed the heck out of it. Needless to say about a day later Check Engine light on. Scanned and sure enough Knock sensor. So I replaced them both, yep under water. So I used silicone to seal the ports when I replaced the covers. Anyway anytime your check engine light (CEL) is on you lose fuel economy. After your vehicle reaches operating temps it goes into "closed loop" meaning the computer reads all the sensors and adjusts the way your engine runs. CEL on means your vehicle stays in "open loop" and runs off pre set perameters in the computer, hense lower MPG's.
    "If it ain't one thing, it's a mother******g nother"

  8. #8

    Default

    Well i now have some water dropping out of my exhaust pipes so... Gotta change those head gaskets anyway.

  9. #9

    Default

    Are you losing coolant? Your exhaust will always drip moisture because of the heat cycles it goes thru. Condensation forms when it goes thru that cycle. If your not losing coolant or oil and you did a compression test I don't know that I would change head gaskets.
    "If it ain't one thing, it's a mother******g nother"

  10. #10

    Default

    Quote Originally Posted by dedmon27 View Post
    Are you losing coolant? Your exhaust will always drip moisture because of the heat cycles it goes thru. Condensation forms when it goes thru that cycle. If your not losing coolant or oil and you did a compression test I don't know that I would change head gaskets.
    Also, water vapor is one of the things that modern catalytic converters end up producing during the chemical catalyst process. It condenses as it exits the system, which results in small amounts of water coming out the tailpipe.

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