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I cannot seem to get a definitive answer wether this cataliyst is restricted or not.
In this thread, I found that the engine isn't breathing right (many thanks to Les byt the way). MAF readings are low which could point to a restricted exhaust, so I came back over here to figure things out. https://blazerforum.com/forum/2nd-ge...ystery-104363/
Another problem that lead me back to this thread was one I started last night trying to do a CKP variation relearn. All of those details are outline in this thread. https://blazerforum.com/forum/2nd-ge...-wrong-104433/
So, onto the back pressure test again. Before I was getting mixed results. Based on the service manual George provided, the number seem to check out, but I'm still skeptical. Did another back pressure test and more or less the same results. I recoded a video this time so everyone can see exactly what I see. The guage reading is on the cusp of it indicating a problem, so I'm not sure what to make of it. I'd hate to throw a new catalyst on and still have the same breathing and acceleration problems.
I also tried driving aorund with the O2 sensor removed, but like before I can't tell a power difference. The noise might be changing my driving habit, so I might be throttling myself.
The book says the back pressure is fine, but my gut is telling me otherwise.
ETCG does a temperature test in this video, and he state that the catalyst inlet should be much less hot than the outlet.
In my temperature test, I find that both are the near same temperature.
Does that give me a definative asnwer?
There's also the procedure in checking the rear O2 sensor. I seem to get mixed results on that data too. I can't tell how much ocellation is acceptable in determining a bad catalyst. I'm not even sure if this method asnwers wether or not the exhaust is restricted.
Here's the data I recorded for another thread showing the O2 sensor with everything warmed up. https://cimg4.ibsrv.net/gimg/blazerf...84f148e38b.png
Does that B1S2 graph look normal? Brand new O2 sensor, by the way.
Another method I tried is knocking around on the pipes again. I think I hear a rattling, but I doesn't have a trained ear to know what broken substrate or a collasped wall would sound like.
I recorded that video here hoping the microphone is good enough. I don't think I hear anything.
Video: Inspecting the exhaust pipe: https://drive.google.com/file/d/1Nzi...ew?usp=sharing
The 2 other methods I have not done is using a pressure transducer like Eric O does in this video:
1) Restricted exhaust gas flow due to the internal honeycomb matrix being physically plugged with debri such as the catalyst metal flaking off
2) The catalyst metal has been exhausted and no longer removes pollutants from the exhaust stream and the truck wont pass inspection. The exhaust may or may not be restricted
3) The cat cannister has a hole in it and causes an exhaust leak, the opposite of a restriction
Those three things can be independent or can occur in combinations. All of these tests that you have discussed address 1 and 2 and therefore some of those tests are not just testing for a restricted exhaust.
A spent catalyst is tested by things like:
1) A post cat O2 sensor waveform compared to a pre cat sensor waveform
2) The pre and post cat temp comparisons
3) An oxygen storage test after inducing an air leak
A plugged cat can be confirmed through a variety of ways such as:
1) Back pressure testing
2) Removing a pre cat sensor and run the truck
3) Vacuum behavior at different rpm's
4) Volumetric efficiency calculations
Yes your performance complaint can be a restricted exhaust but it can be other things as well. You passed the back pressure test and your truck did not run any better with an O2 sensor removed. Did you also test the vacuum behavior to confirm? I think you did a full throttle 1-2 shift MAF measurement on another thread. Your result was low but I don't know the operating conditions. Put that and the associated parameters in to a VE calculator and see what you get. There can be more than one reason for a poor result there but its another data point. I get the feeling that you really want to have a bad cat. Be careful, in problem solving its a bad idea to go into the problem with an assumed cause and winding up closed minded about the data.
I will let you and Les finish with CPK relearn on the other thread.
