Diagnose

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1. OBD  O2 Sensors good reading if

02 Sens upstream  (#1) bouncing between 0v - .8v

02 Sens downstream  (#2) steady around .5v  (bouncing rapidly is bad)

 

**** Catoletic converter info

Good Cat: when sensor 2 is showing a relatively even signal. 5 to .8mv

Bad Cat: when sensor 2 is showing same type of wave form as sensor 1

 

2. Diagnose with aTemp gun.

Engine hot or run 2000 rpm 5min to heat up converter

Get temp of exhaust entering Cat & Exiting Cat. 

  Cat Good if the outlet is 10% hotter than the inlet.

 

3. Diagnose with a bump (The Bang test) 

Cat Bad if it rattles like marbles

 

4. Back-Pressure test. Using a front o2 bung hole or drill a small hole.

       Cat Good hot at idle back-pressure should be less than 1.5psi

        Cat Good hot at 2500rpm back-pressure should be less than 3psi