Sure, I could see a clog in the catalytic converter causing issues idling. If there is a restriction, there is more resistance to getting the exhaust out of the engine that could cause a stall. Were there any engine codes? That’s another good indicator of a catalytic converter issue.

Your issue sounded like there might be something up with the idle air control valve. Did the mechanic make any mention of that? How does the van drive once you get it running?

If the previous owner offered to replace the catalytic converter at a shop, why don’t you let the mechanic handle the purchase of the replacement converter?

I brought a 2001 Prius and prior to me buying this car the Cadillac converter was stolen and the previous owner replaced it but the mechanic took about 2 inches off of the new converter. About five minutes after I left the shop the engine light went on and started feeling that the RPMs were sticking and it made that rattling sound that was described in a bad converter. Now the warning light goes on I’m driving it further concerns me. The person I bought the car from is offering to again replace the converter and pay for the mechanic to repair it but I don’t know what to order for the replacement of the converter. I paid less than 3500 for the car and don’t want to put a whole lot into it but really love the fuel efficiency, especially with the gas prices these days. Please help

Take off those cats your self and if you know a smelter there’s anywhere from 3 to 6 thousand dollars for platinum, rhodium, and palladium or recycle to a scrap yard for 300 per cat bmw’s have 2 but if you put your mind to it your cats could possibly pay for the entire car it’s why people steal them and get the easy scrap price but if you knew how to get those metals out and sell it your jaw would drop on how much money they really make on 1 cat why would a scrap yard give you 300 bucks for 1 of the cats? Lol then get 3000 and they do 1000’s at once if they didn’t get 3000 they wouldn’t give 300 for 1 cat those metals are extremely valuable I had to beat up 5 series got 4 cats then scraped them after I took in the cats and got 1200 those yards are shiesty I took in one at a time cause they wanted to give 300 for the 2 cause it came from 1 car anyways go scrap them you get that money and go buy new cats and still have a ton of money left over and purchase the tools needed and new tires lol

Catalytic converters are valuable, even used ones. I don’t think you should have to pay a fee, and you should be able to ask to get it back if you want it.

The dealership should have waited for authorization before proceeding with the maintenance. That sounds like it may have been a miscommunication between you guys.

I don’t know that aftermarket spark plugs are necessarily causing issues. Could be an issue with the catalytic converter, as those are common codes when you have a bad cat. Probably isn’t the O2 sensors since they just replaced 3 of them, but perhaps.

Why did they only change 3 spark plugs?

Did you get the P430 code figured out? I have tried everything you described and no solution.