Question about testing catalytic converter

[georgewe4]

I took the ZR2 to the muffler shop this morning to have the exhaust from the converter back replaced. The man comes back in after having the truck in the bay for about 10 min or so and tells me that my converter is not working. I asked him how he knew that, and he told me they tested it with a laser/infrared thermometer. The converter was cooler at the back exhaust side than the inlet. I use this type of thermometer alsmost every day and I know they are not accurate on metalic or shiney surfaces, but I didn't say anything.I just thought a truck having over 170,000 miles on the original cat could have an inefficient cat. I also thought that since the exhaust was being done I may as well have the cat done. It would be cheaper in the long run if it would fail later on. One less worry.
The truck does seem to run much better. I just have a problem with the way it was tested. I saw the old converter. The honeycomb material looked perfect in it, and there was no rattles (nothing broken inside).
I wanted my old converter and they told me I could not have it because it is considered hazardous materials, and they would be liable. I was kinda upset by that and I told him it came in on my truck and the converter was mine, but he wouldnt budge. Is the stuff in a converter hazardous? Does anyting here sound fishy??????

 

[myclone]

I use this type of thermometer alsmost every day and I know they are not accurate on metalic or shiney surfaces, but I didn't say anything.I just thought a truck having over 170,000 miles on the original cat could have an inefficient cat.

I use one too and they arent very accurate at all on anything even remotely shiney. Then again with 170k miles the cat may have been on its way out.

I wanted my old converter and they told me I could not have it because it is considered hazardous materials, and they would be liable. I was kinda upset by that and I told him it came in on my truck and the converter was mine, but he wouldnt budge. Is the stuff in a converter hazardous? Does anyting here sound fishy??????

I cant quote any actual law or haz mat litrature but used cats arent supposed to be available to John Q Public and I suppose thats the reason you cant buy a used cat at a salvage yard.

 

[gofstbuick]

The cat needs to be at operating temperature before administering a temp test and iding (high or low idle speed with no load) doesn't bring the cat to operating temp, Some air injection systems can cool the cat out of operating temps. There really needs to be some type of engine load for three minutes after the engine reaches operating temp (60 mph run for three minutes and immediately pull to the side of the road and use a non contact pyrometer front and back of cat; temp should be hotter by at least 100 degrees at the back, review your HS chemistry book to understand catalytic events). A more efficient test is CO2 measurements with a 4 gas analyzer. Also, because the cat uses O2 during the oxidation process (changing CO and HC to H2O and CO2), a quick test is if the O2 content is above 0.3% at idle and 2500 emissions test, the you may suspect the cat, as long as the engine management is in fuel control.
EPA prohibits the sale of used cats, hence the reason for the muffler shop keeping the cat. Only thing in them are a substrate material coated with rhodium, platinum and palladium (sp)

 

[georgewe4]

Thanks for the replies. I was able to drive the truck for some pretty long distances this weekend. The truck runs much better and I noticed something very different as well. After driving the truck for more than 50 miles it would just quit on me. I could be driving down the road and it would completely shut down. It would take several attempts and sometimes it would start for a few minutes, and sometimes it would start and run for a few minutes. I would have to basically limp home at times. Sometimes it would only act up a few times but I knew I had better get home. I was going to post about this but since the converter has been replaced I drove it about a hundred miles yesterday in hot weather with no problems whatsoever. I don't understand it. The truck also has a lot more pep. I had a 2000 zr2 with a 4.3 vortec and it had plenty of power. This one never did until the converter was replaced. Its a different truck. It doesn't make sense that a converter would stop the stalling problems but it seems to have done it. UNLESS, and I could be completely off on this..but would the MAP sensor had been sensing too much pressure with a partially clogged cat and shut the truck down after an extended amount of time? Or some other sensor? There was no check engine light. Just food for thought.
George