Here, we’re covering an idle speed issue on a Grand Marquis. This video goes along well with chapter 20 in my book “Idle Speed Controls”, but also specifically covers Ford scan data and minimum idle speed adjustment. The testing methods shown will apply to most Ford systems that utilize a two wire IAC valve, as well as other 2 wire IAC valves used by other manufacturers.

Engine Performance Diagnostics chapter 20

symptoms 50

  • high idle speed
  • check engine light (P0507)

fix 50

  • adjusting minimum idle speed

test shown enh 50

  • understanding the meaning of a P1000 code and how to inform the customer about it
  • using scan data to diagnose an idle issue
  • how to identify a misadjusted base idle screw using TPS signal
  • how to adjust minimum idle speed on a Ford
  • how to use IAC duty cycle to determine what the computer is trying to do with the idle speed

Tools used

  • scan tool

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(Chapter 20) Idle Speed Problems and Testing

Related videos:

How to test an idle air control valve (IAC) using a Picoscope - Ford:


P0506 IAC System RPM below expected (vacuum leak) - Ford:


Ford idle air control valve (IAC) test - stalling problems:


P0507 Idle Control System (RPM Too High) - vacuum leak - GM:


Honda-Acura Surging Idle Speed (case study):


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For more information on this topic, I have written a “field manual” called Engine Performance Diagnostics which is available as an eBook or paper book.

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