why am I on my 4th catalytic converter?

BAD GAS, ? ARE YIU USING THE SAME BRAND OVER AND OVER, IMPROPER WARN UP......HERE IS SOME HELP FOR YOU> http://www.ebay.com/gds/Reasons-for-catalytic-converter-failure- /10000000002803746/g.html

I agree 100% ... bad gas .....Kelly nailed it. Use Brand Name gas. Chevron, Shell etc, Gas from convenience stores that costs maybe 50¢ a gallon less will cost you more in long term

http://www.toptiergas.com/retailers/ -- these retailers sell gasoline that has detergents and additives your car needs. There are EPA and NHSA and National Highway Safety and Transportation Board standards for gasoline to be allowed to be sold in the US but in my opinion they are not strict enough

Kelly, just read the article from your link. Very good information, I learned a lot and sandie48 highly recommend you take his advice and read it

Once, twice changing cats ... maybe but 3 cats is very rare and 4 catalytic converters (unless you drove a bazillion miles) IMO is very,very,very rare ... In fact I would bet that no one in here has ever worked on a car with that complaint, Are the converters failing due to blockage or burning out? Have you ever had a check done on inlet/outlet temperatures? Something like 275 front and 375-400 back would be acceptable. (((https://grabcad.com/questions/what-is-the-starting-ending-temperature-of-catalytic-converter))) Anti-freeze leakage from a damaged gasket may be the culprit ,,, I say that because GM had a major problem with your cars engine for 2 years when they went to a different anti-freeze (it dissolved the gaskets) .. Of course only the cars that had that problem were repaired so if the problem didn't happen for a few more years then they may not fix it. Cats should last a long time but it's true that gas and other factors will ruin one .. 2 maybe but not 4 Read the link

I don't know if your car, 2003 Buick Rendezvous CXL, has an air/fuel sensor in the exhaust stream.... NOT to be confused with o2 sensors - which measure a similar thing but not exactly, the 02 sensors measure just that, the amount of oxygen in the exhaust stream---- some cars have air/fuel mix sensors in stream and I can not find one at parts places for that car, but have you had your CEL, Check Engine Light on and been ignoring it? No need for me to repeat what Tom says, but it's accurate. If your o2 sensor(s) have failed and are sending false signals to ECU your engine will run either too rich or too lean, and bye-bye cat. In no time.

Yep Tom (the other Tom -D) nor have I. They will last the life of the car or 300,000 miles, whatever comes first. And Tom H, it's not opinion its fact. We could really use some feedback from sandie48

As we speak I'm testing an "in-line" device that will give a direct readout of O2 output (optimum 500 Milli-volts) ... it also can amplify to artificially lean the engine (Temporarly) in order to burn off a light coating on the cat and it also checks the heaters ... (that will give a CEL if open) The simplest way to determine the health of any converter is a temperature differential It's essential that the cat's discharge is at least 100 F hotter then at the inlet manifold

Can some one help me my 03 buick rendezvous is shaking as if it wants to turn off I went to autozone came back to change spark plugs and wires did that and went back same codes it does it mainly when I'm at a stop sign or in drive with foot on brake

Your on a page that hasn't been used in over a year ... how did u even access this page? What codes are you talking about ??? Give us the codes