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Posted: 9/19/2014 1:19:30 PM EDT
[#1]
Page 2 says replace the O2 sensor first because it's way cheaper. |
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Posted: 9/19/2014 1:29:52 PM EDT
[#2]
Do you have a K&N filter? Or any like it that use an oil to keep the filter effective?
If so, Clean or replace your MAF. Replace the filter with a stock filter for the test. |
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Posted: 9/19/2014 1:32:35 PM EDT
[#3]
OP, do you get "free retests"? If you do, start with the O2 sensor and if not do it and the cat before paying for a retest. Another posted mentioned the thermostat and NOT (normal operating temperature).. Make sure the upper hose is pressurized before starting a test. T-stat should have been replaced with the rebuilt engine, but aren't always.
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Posted: 9/19/2014 1:43:04 PM EDT
[#4]
Quote HistoryQuoted:
OP, do you get "free retests"? If you do, start with the O2 sensor and if not do it and the cat before paying for a retest. Another posted mentioned the thermostat and NOT (normal operating temperature).. Make sure the upper hose is pressurized before starting a test. T-stat should have been replaced with the rebuilt engine, but aren't always. 1 free re-test I think within 15 days. I will check the hose and also check the Temp switch which tells the ECM to go ahead and get into closed loop mode. Should be open when cold and have continuity when engine is at operating temps. |
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Posted: 9/19/2014 2:28:27 PM EDT
[#5]
Some of the guys on the Chevy truck forums will replace the ECT sensor about every 5 years. O2 is my recommendation, I just did mine on a 91.
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Posted: 9/20/2014 1:48:14 PM EDT
[#6]
Quote HistoryQuoted: 49 state cats last one year in my experience. The Cal cert cat has more material in it and has been proven by pros to last longer. |
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Posted: 9/20/2014 1:50:05 PM EDT
[#7]
But they never do. You may get it replaced under warranty, but the supplier wont cover the labor.
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Posted: 9/27/2014 9:19:25 PM EDT
[#8]
Just following up on this thread. I ordered a walker universal cat. carb certified since I found it for $100 plus the o2 sensor. When I took off the stock cat it was hollowed out. No wonder why it failed. Installed it and am going for retest next week.
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Posted: 9/27/2014 11:54:30 PM EDT
[#9]
Nice.. Please keep the thread updated!
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Posted: 10/1/2014 11:55:00 AM EDT
[#10]
Truck has been fixed as far as emissions go. Cat converter / O2 sensor combo did the trick.
High idle CO dropped to .19 Low idle CO dropped to .12 |
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Posted: 10/1/2014 12:03:56 PM EDT
[#11]
 cool. glad you're up and rolling.
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Posted: 10/1/2014 12:06:15 PM EDT
[#12]
Quote HistoryQuoted:
Rebuilt new engine. Doesn't smoke or consume oil. Doesn't run hot, idles fine and runs decent. As far as I know, O2 sensor is stock. So it's never been replaced. Quote HistoryQuoted:
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What engine? How many miles? Edit: 380k miles? When was the new engine installed? lol. 5.7L New engine installed at 300K Now we are getting somewhere. New engine or new to that truck or rebuilt new engine? Also, as the poster above mentioned, when was the last time the O2 sensos were replaced? Folks are going to get tired of the guessing game pretty quick. Rebuilt new engine. Doesn't smoke or consume oil. Doesn't run hot, idles fine and runs decent. As far as I know, O2 sensor is stock. So it's never been replaced. Get a new one, they don't really last longer than 120k. 
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Posted: 10/1/2014 12:07:57 PM EDT
[#13]
Quote HistoryQuoted:
Truck has been fixed as far as emissions go. Cat converter / O2 sensor combo did the trick. High idle CO dropped to 19 Low idle CO dropped to 12. Probably didn't need a cat... 
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Posted: 10/1/2014 12:13:18 PM EDT
[#14]
Quote HistoryQuoted:
Sounds like the catalytic converter has failed. What happens is the monolith breaks free of the shell and grinds against the tail cone reducer, forcing all flow through the center section. When this happens, it works fine on the idle but because of limited area, it cannot oxidize all the CO to CO2. The increased back pressure can cause issues with oxygen sensor output. Pull the converter and shake it, if it rattles, it has failed. You can get a good deal of trade in value as the scrap value is high. Quote HistoryQuoted:
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Don't really want to throw money at this thing blindly. if I replace O2 and Cat and it still fails I'll be at a loss. One thing I forgot to mention to you guys was that when I drove it back after it failed inspection I got underneath the truck to check the CAT. I touched it and i was able to hold my finger on it for about 2 seconds before I had to pull it back. Shouldnt that CAT be so freaking hot that I wouldnt be able to hold my finger on there at all? Things I can do for free first. Inspect Evap can Check EGR valve Spark Plugs reducer, forcing all flow through the center section. When this happens, it works fine on the idle but because of limited area, it cannot oxidize all the CO to CO2. The increased back pressure can cause issues with oxygen sensor output. Pull the converter and shake it, if it rattles, it has failed. You can get a good deal of trade in value as the scrap value is high. I agree, sounds like the cat won't stay lit up.. replace the cat and the o2 sensor..should be good to go.. |
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