help! broke student + no auto repair knowledge + repair shop possible mistake?

[cardummy7]

Hey all! I'm new here and know nothing about cars (as per the username ). I'm hoping someone can help me out with this. Thanks in advance!

So I have a 2003 Corolla that has been running beautifully for years. No major issues. Then all of a sudden, my check engine light comes on. Bring it to a friend's repair shop (we will call this repair shop A), apparently it's my cat converter. They don't charge me for labor, but I paid 517 for the replacement piece (which my limited internet search tells me that it means it's a decent piece?(in nyc/nj))

A week later the light comes on again, and I bring it back to repair shop A. The same guy tells me that according to the code, it's probably just some engine gunk (do I buy good gas, go to name brand places that don't water down, yadda yadda, I promise I do!). He throws in some tank cleaner that should fix it.

A month later, my battery and engine light both come on after a major rainstorm. Figured some water got under my car (my area floods). Bring it to another repair shop (dad's friend, he offered to take it for me -- repair shop B), and apparently my engine is misfiring, they replace a cylinder, no problem.

Cue about another month later, my check engine light is back on. Bring it back to repair shop B, and apparently the code means my cat converter died again, and that I should bring it back to repair shop A, because they "owe me a functional one".


Here's the issue (sorry for the long complicated story!!):

Are all of these issues somehow related? Like, did the faulty replacement cat converter cause the secondary issues with the engine? Or vice versa.... did the first shop replace the cat converter while missing the underlying cause of the cat converter failure, leading to the new problems. The reason I ask is because the repair shop belongs to a good friend's family, and I don't want to be rude. But at the same time, I'm a broke student and can't keep shelling out hundreds to thousands of dollars on a car, especially if it's because of someone's mistake.

Any and all help would be appreciated. I have to handle this in the next few days, and I want to have as much info as possible going in, so that I can deal with it respectfully but while maintaining my "rights"?

Thanks guys!

[Brian R.]

Your catalytic converter may be ok. Your problem with the catalytic converter code is likely due to a faulty oxygen sensor which monitors cat converter function. If it tells your computer the converter is bad, it is most likely the sensor, not the cat converter.

Replace the oxygen sensor after the cat converter. Call a Toyota parts department and get a Toyota part number for the sensor (Bank one, Sensor two) with your Vehicle Identification Number (on dashboard). Get the DENSO part number ( http://densoautoparts.com/find-my-part/cross-reference ) using the Toyota part number. Make sure the mechanic puts in the correct DENSO part. Don't settle for any other brand or part number.

Once you get the DENSO part number, you can buy it yourself from Amazon.com using the DENSO part number in a keyword search. Amazon has the cheapest prices I know of. The rub is that many mechanics will not install parts that they don't personally buy, since they make money of off the purchase.

[famlycar]

Isn't there two oxygen sensors? one on the manifold and one somewhere under the floorboards?

[Brian R.]

Yes, there are two. The one before the cat converter does not signal catalyst efficiency. It only controls fuel/air mixture. The one after the cat checks catalyst efficiency.