Maybe a dumb question

Discussion in 'Performance & Fuel' started by rileyjr16, Aug 20, 2013.

  1. rileyjr16

    rileyjr16 Epic Member 5+ Years 1000 Posts

    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.
  2. dobey

    dobey Epic Member 5+ Years 500 Posts

    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. rileyjr16

    rileyjr16 Epic Member 5+ Years 1000 Posts

    Exactly the news I was looking for... New project for the week. [MENTION=44531]Sierraowner5.3[/MENTION]?
  4. McClintoc

    McClintoc ɹoʇɐɹǝpoɯ Staff Member 3 Years 1000 Posts

    Dumb question follow-up: how long do knock sensors usually last or what is a good interval to change them?
  5. rileyjr16

    rileyjr16 Epic Member 5+ Years 1000 Posts

    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...
  6. Sierraowner5.3

    Sierraowner5.3 Epic Member 5+ Years 1000 Posts

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

  7. dedmon27

    dedmon27 Rockstar 100 Posts

    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.
  8. rileyjr16

    rileyjr16 Epic Member 5+ Years 1000 Posts

    Well i now have some water dropping out of my exhaust pipes so... Gotta change those head gaskets anyway.
  9. dedmon27

    dedmon27 Rockstar 100 Posts

    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.
  10. dobey

    dobey Epic Member 5+ Years 500 Posts

    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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