84 Turbo High Idle

  • #1

    84 Turbo High Idle

    Normal idle for a 300ZX with M/T is 700 rpm plus/minus 50 rpm at sea level. When I first purchased this car, it was idling at 1400 rpm. I replaced the Air Regulator, had a gasket replaced on the Idle Air Control Valve (IACV), and made some adjustments to the idle. The most I've been able to reduce the idle is down to 1000-1100 rpm.

    I have performed diagnostics and made adjustments according to the FSM. I even tried swapping in another ECU and a known working IACV from another car. I sitll couldn't get the idle back to normal. From what I know and from what I read in the FSM, I have exhausted all of my options at this point (other than deleting the IACV). Would appreciate any information from forum members who have a lot of experience with engine performance or idle speed issues.

    Cheers
  • #2
    Are you sure you don't have any vacuum leaks?
    Is the ignition timing set too advanced?
    Has the screw on the throttle plate stop been tampered with?

    1986 300ZX Turbo…sold
    1990 Skyline GT-R…new money pit
    2014 Juke Nismo RS 6-speed…daily
  • #3
    Cleaned and lubricated throttle plate stop and IACV. Reinstalled throttle plate and IACV. Ran engine long enough for ECU to relearn idle. Worked perfectly. Engine idle speed is much closer to normal (750-800 rpm).