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George H.
George H., ASE Certified Technician
Category: Car
Satisfied Customers: 18308
Experience:  ASE Master Tech 15+ yrs, AAS Automotive Technology, Factory trained Asian specialist
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2003 hyundai Sonata: cylinder..The check engine light..OBD..catalyst

Resolved Question:

I have a new 2003 hyundai Sonata 4 cylinder. The check engine light just came on. The OBD is reading the "warm up catalyst below threshold bank one". I have just replaced both cv axles and plugs and wires. When i replaced the plug wires the electrode in the number 1 cylinder was seperated from the wire. It also idles with a vibration throughout the car, it's not a rough idle just vibrates the whole car. It runs great just this check engine light and vibration. 4 cylinder automatic hyundai sonata base sedan.
Submitted: 7 years ago.
Category: Car
Expert:  George H. replied 7 years ago.

Hello I will help you with your question,


How many miles on your Sonata?

Customer: replied 7 years ago.
151000 miles are on the car. The check engine light went off. The outside temperature has been fluctuating about 20-30 degrees up and down for the last couple of days. The vibration only happens when i come up to a stop sign/light and leave it in drive, if i put it in neutral the vibration goes away.
Expert:  George H. replied 7 years ago.



Do you know if the timing belt has been changed?


Check the motor mount at the top right side of the engine by opening the hood and rocking the engine bak and forth in reverse and drive with your foot on the brake. these are known to go bad and cause vibration.


Was there any oil in the plug wells when you changed the wires? Did you change the boots on the coils or just the wires? What brand of spark plugs did you use?

Customer: replied 7 years ago.
There was no oil in the wells and the plugs looked pretty good for the miles they had on them. There are two coils on the engine, i replaced the number 1 coil and all the wires were replaced with new ones. The boots were replaced as well. The plugs were the advance auto brand, Duralast.
Expert:  George H. replied 7 years ago.

I am not familiar with who is making AZs plugline but Hyundais are pretty picky about their plugs an only like NGK or Denso as a rule. I dont think this is all your shake, these were never the smoothest engines but if this is not the third timing belt and balance shaft belt you need to get that changed as soon as possible. when the belt teeth strip off the valves will be damaged. The balance shaft may be out of time due to the teeth stripping off its drive belt or may have been put back out of time on an eariler belt replacement so change the belts and the mount at the same time.


If the code was for the cat it may need to be replaced as the misfire may have melted it but that would show if you rev to 2500 and held it there it would start to choke


The first step I would take is to have the codes read and check the mount.


Plan on replacing the belt and mount if the belt has not been changed.


Let me know what codes you come up with

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