Anytime you have idle speed control related trouble codes (P0505, P0506, P0507) the first thing you want to look for is a vacuum leak. Many idle air control valves, solenoids, motors and electronic throttle bodies have been replaced needlessly due to these trouble codes. In this video we will focus primarily on fuel trim data to determine if we have a vacuum leak. LTFT values will be shown at different RPMs to give us a clear direction.

Engine Performance Diagnostics chapter 4

symptoms 50

  • check engine light (P0171, P0174, P0506 trouble codes)
  • rough idle
  • poor gas mileage
  • hesitation on acceleration

fix 50

  • replace EGR valve (worn pintle)
  • intake manifold gasket (leak)

test shown enh 50

  • how to interpret idle speed control data
  • how to interpret electronic throttle control data
  • how to use fuel trim data to identify a vacuum leak
  • how to smoke test an intake manifold
  • fuel trim data at different RPMs

Tools used

  • scan tool
  • smoke machine

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(Chapters 4 and 5) Fuel Trim and Oxygen Sensor Testing

Related videos:

P0507 Idle Speed Performance Higher Than Expected (vacuum leak) - Jeep:


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


False mass airflow sensor/idle control system codes - vacuum leak :


Chapter 20 "Idle Speed Controls" - preview (an SD Premium video):


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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.

Want even more diagnostic training? Whether you are a DIY trying to fix your own car, someone looking to become an auto technician, or a current auto technician that wants to get more into diagnostics, subscribe to ScannerDanner Premium. There is a 14 day free trial.

On ScannerDanner Premium I will bring you right into my classroom at Rosedale Technical College. You will find page for page lectures taken right from my book as well as exclusive classroom type case studies. What is so special about these classroom case studies? I pull live problem vehicles directly into my classroom and we troubleshoot them in real time, using and applying the theory and testing procedures we learn during the classroom lectures. There is no better on-line training of how to troubleshoot automotive electrical and electronics systems anywhere!