Zafira 1.6 unsteady idle bouncing revs

  • ZaffyB's Avatar
    Zafira 1.6 petrol 80k engine Z16XE1

    I’ve noticed my rev counting bouncing up and down about approx half a centimetre .. and the engine lumpy on idle. seems to fluctuate when warm but most of the time it does it.

    Had a full service. The pollen filter has t been changed in two years on my list.

    what are the usual suspects for this kind of issue ?

    p0115-15 engine coolant temperature sensor circuit range/performance <---would that cause my symptom's?)

    p1571-00 brake switch circuit malfunction (this was checked last year at the garage and they said there was no fault and that my brake lights were all good) no stuck brake lights on or off. They cleared it but it came back repeatedly.

    Both cleared and 48 hours later only the brake light witch dtc came back.

    After a 25 minute drive the thermostat reading was sitting between 68-77 whilst driving (outside temp 6.5)

    when left idling It went to 101 before I turned it off normally sits at 105.

    The heat out mild on the blower on full heat and speed, that said it is cold :)

    After the drive I noted the following on idle

    coolant temp 87
    Radiator coolant temp 80 (1.60v)

    not sure these two temps should be as close ?

    I've attached a live data scan and a scan at idle. The live data is a bit of a blob of everything the other shows readings fine.

    Thanks for any help, bit stumped.

    https://easyupload.io/d8ixnj
    https://easyupload.io/pt3rhx
  • 3 Replies

  • wagolynn's Avatar
    Guest
    Looks as though the engine temperature sensor has failed.

    Also the radiator fan should have kicked in when engine temperature was high - I think, there is a separate sensor/switch for that on the radiator (it will have wires to the fan)
    Last edited by wagolynn; 03-12-20 at 17:34.
  • ZaffyB's Avatar
    UPDATE: After a 25 minute drive the thermostat reading was going between 68-77 whilst driving (outside temp 6.5)

    when left idling It went to 101 before I turned it off. Usually gets the 105.

    I rescanned the car and the coolant code didn’t come back.

    The big hose going in to the thermostat get hot quickly not long after driving. I assume this should get hot until it hit 105 (when the thermostat is suppose to open) ?

    After the drive I noted the following on idle

    coolant temp 87
    Radiator coolant temp 80 (1.60v)

    If I leave it idling coolant temperature gets to around 105.

    if I’m driving it going between 68-77.

    Oddly the coolant temp sensor fault has t come back after clearing.
  • ZaffyB's Avatar
    I put a new thermostat in today, bled it and no leaks and roasting hot heater. The temperatures get where its need to.

    but sadly the unstable idle is still there :-(

    it did for a millisecond cut out on me while driving which is new! But didn’t stall and came alive to carry on driving without stopping. Weird all the needles dropped to 0. Literally a millisecond. Nothing in opcom.

    From searching it maybe my Delphi coil pack not being genuine despite working for 3 years. Apart rly this engine doesn’t like non genuine parts. A genuine one is about £189 so will hold off till I can positively figure it out.

    any help would be welcomed at this point