Treated car good hoping to get 200,000 miles or more. Changed catalytic converter (clogged) 95k and timing belt! To get most out of car. Nothing but issues since P0420 coming on all the time. Anyone having similar issues and problems. Mechanic tried everything that worked with even some freebies. Tried a case # with gm no help due to fact over warranty. Mechanic thinks probably a software issue and thinks should be lemoned out! Any ideas? Thanks!

 

Is your Sonic misfiring, using oil, running rich or lean or anything else?

 

mechanic did state misfiring during bringing back for catalytic converter warranty. No other problems mentioned by mechanic. Frustration set in along time ago wish GM/Chevy take a little more ownership. Understand over warranty but replaced parts and major CEL LIGHT ISSUES!

 

Things like misfiring or motor oil burning will destroy your catalytic converter. So can the "PVC" system, which is a bad overcomplicated system. Back in the day, you pulled the PVC valve off the valve cover, chucked it in the trash, and installed the PCV valve, total time, 15 seconds.

This Youtube video should help you out, Jeff:

 

[QUOTE=Jeff Hanson;453668]Treated car good hoping to get 200,000 miles or more. Changed catalytic converter (clogged) 95k and timing belt! To get most out of car faulty oxygen sensor or loose gas cap

 

[QUOTE=chevyboy@22;453741]If you have too much pressure in the motor, sooner or later seals and gaskets are going to blow. You need to remedy this now.