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Excess carbon during long idle

Discussion in 'EEK! - Every Extended-K Car' started by goair99, Dec 26, 2017.

  1. goair99

    goair99 Active Member

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    I have a '94 LeBaron sedan 3.0. I have noticed lately that there is excess carbon in the exhaust after the engine idles for five or more minutes. The exhaust is light grey and smells foul. It does not have any blue in it. Any ideas? This is not oil burning, I know my car does not burn any oil.

    The engine runs very smooth, and this carbon exhaust disappears during normal driving. It's only when she idles for a long period of time. She has 117K on her with the original O2 sensor in her.
     
  2. ImperialCrown

    Level III Supporter

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    If not oil, is it idling too rich?
     
  3. goair99

    goair99 Active Member

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    Yes, that is what I was thinking. Could the original O2 sensor cause this? I burn non ethanol 87 octane gas in her.
     
  4. valiant67

    valiant67 Rich Corinthian Leather
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    The mixture can be off, but the O2 sensor not bad enough yet to set a code.
     
  5. goair99

    goair99 Active Member

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    How is the mixture controlled? I went ahead and ordered a NTK 02 sensor from rockauto, she has almost 117K on her. I will also have my guy check her out when I have the trans and engine mounts replaced. 20170525_111401.jpg 20170525_111408.jpg 20170525_111419.jpg
     
  6. valiant67

    valiant67 Rich Corinthian Leather
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    The mixture is controlled by the O2 sensor, though there are some other inputs (like the coolant temp sensor which tells the computer to richen the mixture when the engine is cold).
     
  7. manybrews

    manybrews Active Member

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    You're describing the perfect scenario for visible oil from the exhaust via the valve seals, though.

    Extended idling allows the oil to dribble into/onto the valves and combustion chamber, then burn off (particularly when the revs are raised).
    You sure its not oil?
     
    valiant67 and Bob Lincoln like this.

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