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Thread: how to adjust idle?

  1. #1
    Join Date
    Nov 2009

    how to adjust idle?

    Hey all..

    is there a way to adjust the idle on a v8 discovery, basically when i start mine up.. it will rev low and occasionally turn off when cold, you have to hold the revs up abit otherwise she will stall... on idle it sits at about 550rpm, which i assume is too low...

  2. #2
    Join Date
    Jan 1970
    Adelaide Hills. South Australia
    3.5 or 3.9 Efi?

  3. #3
    Join Date
    Jan 1970
    Avoca Beach
    Both the 3.5 and 3.9 have 14CUX so the issue is the same.

    The idle is controlled by the ECU so you cannot/should not adjust it. the air let through is controlled by the stepper motor which is controlled by the ECU.

    The first thing to look at will be the ECU temp sensor to see if it is giving the correct signal to the ECU. When hot it should show 300 Ohms or thereabouts and cold much more maybe 1000 Ohms. The sensor is the one behind and to the right of the thermostat and it has an injector plug on it .

    The next thing to look at at would be the stepper motor, which is that thing on the RH back of the Plenum chamber with 4 wires running to it. Carefully remove the plug, unscrew the stepper and clean the cone shaped thing with carby cleaner and put some on a qtip and clean inside the housing.
    Maybe also take of teh pipe from the MAF to the throttle and clean around the throttle plate with carby cleaner and a rag.

    Try that first and report the outcome.

    Regards Philip A



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