The break in period for a new Catalytic Converter is between 50 and 100 miles, AFTER an initial "warm-up period" which should be administered as follows:
- Start engine. Do not step on gas pedal.
- Idle engine and allow slow warm up; allowing for metals to expand and sit in place.
- After approximately 10 minutes, increase the engine speed to 2000 RPM.
- Hold engine idle at 2000 RPM for 2 minutes.
- Return engine to Idle and allow the engine to cool down for 5 minutes.
So having driven your Chevy Malibu for over 100 miles should have completed the CAT break-in. The only other thing to consider in this matter is whether or not your Chevy Malibu's check engine light was reset during the catalytic converter replacement. If it was you'll need to make sure that the check engine light is now turned off and that the "emission monitors" are in READY status. Having driven for 100 miles should have completed the emission monitors (these are internal self-tests that the ECU performs to ensure your Malibu's emissions system is functioning properly). If you're unsure ask a smog technician to check the emission monitors before the smog test.
