Temps on catalytic converter

[Dave]

I watched Eric’s video on checking a catalytic converter and from what I understand, the temps should be the same at either end.

I tested mine at the inlet right before the heat shield and at the outlet just as the pipe starts. I got temps of 290+/- inlet and 130+/- on the outlet.

This is on a ’95 Cavalier if that matters.

Does this look like a bad cat?

-Thank you.

OH! A couple of months ago, I was driving and no matter how much gas I gave it, I couldn’t go faster.

BUT – when I shut the car off and drove again, the problem went away and hasn’t appeared again.

Topic

[Steven Cummings]

Your temperatures are very low. The outlet temperature should be much higher on your out (around 500-800C)

[Dave]

OK. So, the temp difference is indicative of a bad catalytic converter?

[EricTheCarGuy]

You might want to re-watch the video.

As it states the temp on a working converter should be 100ºF hotter on the outlet than the inlet. You also need to bring the car up to operating temperature when you do the test. Given your readings I’m not sure you did that.

[Steven Cummings]

Also, If you don’t have a code…don’t worry about it. Don’t look for a problem where there is none.

[Dave]

OK, thanks.

BTW, it was at operating temperature

[Dave]

I failed emissions with high NOx and HC.
And my car’s ECU didn’t throw a code. Anyway, it’s really hard to check since I have GM OBD “1.5” – those !^%#@%#&@&!!! Thanks GM!

The basics checked out – clean air filter, fuel pressure regulator, plugs, wires, etc …

My O2 sensor (I have just one) was giving weird voltages at idle (+650mV). When I pulled it, it was UGLY – lots of white crusty crap.
That was probably antifreeze residue from before I put a new head gasket in.

And I had some backfiring issues a couple of years ago.

SOOOOOOOO … all of that probably toasted my CAT.

I got a new one coming in about a half hour from now for $128.

[Dave]

Alright – get this.

I just pulled my cat. And it rattled. Looking in, the medium looked like this chuck of eggplant sized …stuff.

And it moved around by just tilting it.

So, here’s my theory about why I had that issue with no power a month or so ago.

That chunk of junk rattled around to the outlet or inlet and blocked it. And when I stopped, it settled down and allowed for the exhaust to go through.

Allowing for everything to work fine again.

[Steven Cummings]

Glad you figured that out. Sorry about the emissions test. I have one coming up myself. Should have remembered yours was not OBDII and not as robust on the codes.

[Author]

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