2000 Mazda Miata catalytic converter

catalytic-converters
miata

#1

I have this vehicle, which keeps blowing out the catalytic converter, its been replaced 3 times in the last month, and the mechanic doesnt know why, he refuses to put another one on it, until he figures this out. Can you help?


#2

Yes, the Bricklins were known for this.

What? You say you don;t have a Bricklin? Well jeepers, what Do you have?

PostScript: I owe you an apology. Your year make and model were in the heading. I missed it. Doggoned bifocals. Sincere apology. Please forgive me.

Now to the question at hand. How, exactly, is the cat converter “blowing out”?
Are the substrates crumbling?
Is the catalyst becoming coated? With what?
Is he changing them just based upon the OBDII code?
Has he changed any other parts?
Has he put the engine’s oxygen sensors on an oscilloscope to look at the actual outputs?

Crumbling substrates would suggest extreme heat and shock. There should be other symptoms along with the CEL. And there should be other codes.

If the catalyst is becoming coated, the source of the coating needs to be ascertained. Oil burning?

If he’s just readng an OBD code and changing it based purely on that, you need a new shop.

Please post back.


#3

Are you having any other symptoms or check engine light issues? The 1999 & 2000 Miatas were well known for coil packs to go out for a variety of reasons and demolishing the converter in short order.

If you’ve washed your engine recently these cars are known to capture water in the spark plug wells which leads to arcing with leads to coil pack failure which leads to catalytic converter failure.

The problem can be that the coil packs don’t stay broken and can be intermittent, it only takes a few seconds of misfiring for the converter to be poisoned in these cars.


#4

Ladyntejas, I posted this to another thread that you had joined, but I’ll happily copy it to this one.

A crumbling ceramic substrate suggests extreme heat and/or shock. Extreme heat usually comes from lean operation…analogous to using a bellows in the fireplace, the extra oxygen makes the fire hotter. This should, however, post a fault code.

Another possibility is heat buildup, like if the exhaust past the cat converter is restricted. This can be tough to diagnose because the engine will run fine at idle, but when it’s running restricted at 3000 rpm the heat builds.

Have you experienced any other codes? If so, post them.
Does your car have a resonator in the exhaust system? Perhaps that’s plugged.

I’m not generally a fan of throwing parts at a problem, but a partially restricted resonator or muffler can be tough to find. And it won’t post a failure code. In your case, since you’ve had three converters collapse and apparently diagnosis has been unsuccessful, you may want to suggest to the mechanic that he replace the rest of the sxhaust system.

Your problem is not the same as Federal102’s, but I’m glad you joined the conversation. Hopefully we can help you both.