In this video I will show you how to test to see if your catalytic converter is plugged or restricted. I will be showing you an exhaust system with a plugged cat. and will compare the results to a known good exhaust system. I will also show some alternate locations to perform an exhaust backpressure test.

Engine Performance Diagnostics chapter 1 pages 8 & 28

symptoms 50

  • very low power
  • cannot accelerate past 30 mph
  • pinging under load
  • transmission doesn't shift right

fix 50

  • replace catalytic converter
  • repair any misfire and fuel trim issues

test shown enh 50

  • how to test exhaust back-pressure
  • exhaust back-pressure test using an EGR pressure sensor port
  • exhaust back-pressure test using the upstream O2 port

Tools used

  • exhaust back-pressure test kit
  • vacuum/pressure gauge

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(Chapter 1) Misfire ID, Compression Tests, Vacuum Leaks, Fuel Trim, Head Gasket, Restricted Exhaust, Low Power, DMM

Related videos:

How to test for a restricted exhaust using the DPFE sensor on a Ford :


O2 sensor (fixed lean) and restricted exhaust test (melted cat) - GM :


How to test for a restricted exhaust (catalytic converter):


How to test for a plugged exhaust (picoscope & psi transducer):


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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!