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Hi,my Toyota Celica 2001 Vvti 140km ,The computer shows the misfire on the second and third cylinders and P0300 and error P0420 occurs from time to time,the engine wobbles at low revolutions,especially when it warms up Please help Michael

Answers from the Automotive Experts

Jessica Howe, Automotive Expert & Coach at AskPatty.com

Hello, 

Thank you for writing in. Start by diagnosing the misfire (P0300), as it may be what is causing an issue with the catalytic converter (P0420). There are a large number of reasons why your car may be experiencing multiple misfires. Most common are issues with the fuel/air mixture, the ignition system, or cylinder compression. You may need to check fuel pressure, fuel injectors, spark plugs, air intake sensors, and each cylinder's compression. 

Once you have solved the misfiring issue, which will cause the engine to shake and vibrate, you can re-scan the vehicle for codes to see if the catalytic converter is still showing a problem. A qualified technician will be able to help you if needed. Good luck!


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