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Surging and stall at idle

Discussion in 'Technical, Maintenance and Modification' started by MustangMike, May 16, 2018.

  1. MustangMike

    MustangMike New Member

    My 92 fox has issue with surging and stall starts right up but during stops sometime stalls but always surging between 500 and 200 Rpms
  2. broncojunkie

    broncojunkie Active Member

    There are quite a few things that could cause it, unfortunately. A vacuum leak is normally the culprit, from what I've found. Although, a bad leak normally caused a high idle. Anyway, check all vacuum lines and the seal around your intake... including the rear lower intake where your pcv is located. You can check by spraying a little starting fluid or brake cleaner around the engine bay during idle.

    You IAC valve (idle air control) is another common culprit. Simply remove it from your throttle body and clean it as well as the two openings where it connects. I had to replace one recently and the new one was also bad.

    You can also Google "base idle reset" and go through the process of setting the idle, but you need to make sure all other issues are taken care of before doing that.

    Ignition timing, dirty mass airflow sensor, bad O2 sensor, worn ignition components, and wiring issues can all cause problems with surging idle.

    If you do a search for "surging idle checklist" there is a good one floating around the mustang forums. I've used it before and it was very helpful.

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