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Thread: Open loop

  1. 19th December 2008, 07:57 AM #1
    astormsau
    astormsau is offline Fossicker
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    Open loop

    hey everyone

    bit of an interesting one...

    I have a 2000 V8 D2.
    I also have a scanguage 2 and occasionally check that my car is running correctly by checking for fault codes and checking all the readings given such as whether the system is running in closed or open loop,etc.

    I had an engine rebuild 2 months ago, I replaced both oxy sensors as they were stuffed when the engine had developed a 2inch crack in the block and spat water out the exhaust...

    About 4 months ago I treated it to a new MAF.

    After the rebuild and 2 new oxy sensors the car has been running faultlessly :- no fault codes, starts in open loop then goes closed once warmed up,etc.

    Now in the last 2 weeks for some reason, it wont go closed loop, it stays in open loop all the time.

    There are no error codes which the scanguage picks up, engine temp reads steady around 90 - 95 degs depending upon condition on the scan guage.

    The motor seems to run fine on petrol or LPG (i have a sprint gas vapor injection system fitted), no noticeable issues and economy is fine - but it just is strange that it always reads open loop - ie it never goes to closed loop.

    I have checked all spark plug leads at the spark plug ends and all are plugged in okay (i havent checked the coil pack ends yet), i have checked oxy sensor connections and done a general visual inspection - all seems fine. I have also ran it on petrol for a while to see if something else associated with the LPG was causing the issue but no apparent issues there. So as i said, no fault codes and no signs of the motor running poorly... im a bit confused...

    Does any one have any suggestions?

    Thanks
    Andrew
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  2. 19th December 2008, 08:48 AM #2
    PhilipA
    PhilipA is offline Swaggie Subscriber
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    Is this on gas or petrol or both?
    If on petrol I would perhaps suggest a faulty water temp sensor which tells the ECU the car is still cold and the enrichment puts the sensors out of range.
    Or faulty thermostat. Is the gauge reading cold?
    Or faulty MAF.(sorry)
    Or air leak at exhaust or inlet.

    Regards Philip A
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  3. 19th December 2008, 10:54 AM #3
    astormsau
    astormsau is offline Fossicker
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    Quote Originally Posted by PhilipA View Post
    Is this on gas or petrol or both?
    If on petrol I would perhaps suggest a faulty water temp sensor which tells the ECU the car is still cold and the enrichment puts the sensors out of range.
    Or faulty thermostat. Is the gauge reading cold?
    Or faulty MAF.(sorry)
    Or air leak at exhaust or inlet.

    Regards Philip A
    Hi Philip
    Happens on both LPG and petrol. I havent seen it go closed loop for weeks now.

    My understanding is the scanguage reads the engine temp from the water temp sensor which is the same one used to send the signal to the dashboard guage. The dashboard gauge shows normal operating temperature as does the Scanguage which runs between 90 and 95 degrees and gradually warms up as usual when the motor starts.

    MAF seems to work fine as the car performs as well as it did when I replaced the MAF and no errors coming up in the cars computer about the MAF or oxygen sensors.

    Could be a leaking exhaust or inlet, all of this gear has been off the car recently and it was working fine once it was replaced, plus generally those leaks manifest themselves as a misreading in the oxy sensors... but as I said, there are no faults coming up which confuses me....

    Andrew
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  4. 22nd December 2008, 01:28 PM #4
    astormsau
    astormsau is offline Fossicker
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    anyone else?

    i tried unplugging oxy sensors and MAF yesterday.. ran the car until it was at operating temp and then turned it off, plugged all sensors back in and cleared codes, seems to go closed loop now as it should but im suprised this happened in the first place, any ideas would be great.

    Thanks
    Andrew
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