New to 308 found something unplugged any ideas what it is? | FerrariChat

New to 308 found something unplugged any ideas what it is?

Discussion in '308/328' started by Popoco, Mar 18, 2021.

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  1. Popoco

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    Ricardo Aguilo
    #1 Popoco, Mar 18, 2021
    First-time posting, first-time Ferrari owner. Already got a lot of use of this site when deciding on a car, thank you.

    Found this unplugged (see attached) while doing the first examination of the engine(Right rear). Any idea what this is used for?
    Side note - The car seems to have an idle problem when it gets to operating temperatures (Still testing)


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  2. SeattleM5

    SeattleM5 Formula 3
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    #2 SeattleM5, Mar 18, 2021
    That's the plug for the oxygen sensor. With it unplugged the jetronic CIS ECU is running 'open loop'.

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  3. Popoco

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    #3 Popoco, Mar 18, 2021
    Thank you, this might be why the car is having an issue with warm idle.
     
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  4. kiwiokie

    kiwiokie Formula 3

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    #4 kiwiokie, Mar 18, 2021
    Often open loop is used to mask an issue apparent when running as designed in closed loop. Hope you are lucky!


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  5. yelcab

    yelcab F1 World Champ
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    #5 yelcab, Mar 18, 2021
    There are two connectors for the O2 sensor. One 2-pin for the O2 heater and a single pin connector for the O2 signal. Find both.
     
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  6. Popoco

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    #6 Popoco, Mar 19, 2021
    Currently, both are plugged in.
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  7. SeattleM5

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    #7 SeattleM5, Mar 20, 2021
    Ricardo, how is the car driving/idling with the O2 sensor now plugged in? As kiwiokie noted, the O2 sensor being unplugged is a sign that the car may have been having issues running closed loop in the past and someone unplugged it forcing the Jetronic ECU into a fixed, open loop configuration. There are a multitude of issues to consider in this situation but I have found one of the most common reasons for someone unplugging the O2 sensor is to solve idle surging issues. When the AFR is out of balance the Jetronic ECU will constantly try and adjust it back to the appropriate stoichiometric ratio by micro adjusting the fuel distributor lower chamber pressure via the frequency valve which results in significant idle surge. The other scenario I have seen is when someone wishes to gain more power by running the AFR on the richer side (i.e. 12.6:1) and by disconnecting the O2 sensor it remains fixed at that ratio and the ECU won't try to adjust back to stoichiometric (14.7:1).
     
  8. Popoco

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    #8 Popoco, Mar 26, 2021
    Ok, so I've been driving it for a few days with the sensor plugged in; the warm idle problem improved considerably but persisted; what did end up helping a bunch was putting ethanol-free fuel in it. Thankfully I had only put a splash of 10% ethanol fuel in it to get it to move after delivery. In summation, the warm idle problem is fixed, and I believe the car is running better with the sensor plugged in. Having said that, yesterday, on a short drive, I got some high water temperatures, and I'm bleeding the coolant system today, hoping it helps(The oil temp remained dead center.)
     

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