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Discussion Starter · #1 · (Edited)
so was on the way home from work and all of a sudden my truck lost power but was still running. pulled over and looked under the truck and saw the cat was glowing orange. let it cool down and limped it 4 miles back to my work (I work in a diesel shop). used 1/8 of a tank of gas just going those 8 or 9 miles and the entire time I could barely accelerate and couldn't get over 50mph.

was throwing a code for the down stream O2 sensor and for the O2 heater. replaced the sensor (advance didn't have the AC Delco sensor in stock so I got the Bosch), and nothing changed. figured the cat was clogged so was going to gut it but some moron in the past cut it off and welded in a universal cat. so I cut an access panel in it and gutted the thing. It's now idling much better but still loosing power on the high end and I can smell the gas in the exhaust even at idle so it's running pretty rich. Also have noticed that no matter if it's a cold start or completely warmed up already, my scanner is reading the O2 sensor is always in open loop even after running for 10 minutes. no vacuum leaks, plugs and wires are OEM and less that 2 months old and don't show any signs of fouling, and no misfire codes.

the only thing I can think of is just replacing both the up and down sensors with OEM parts and hoping for the best. as for having already gutted the cat, I've never done that before so I have no clue if the new sensor will read right even if I get the OEM sensor. any advise here would be great.
 

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2004 Avalanche. 2001 V6 Extended Cab ZQ8.
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If it is stuck in open loop, then you need to figure out why? O2 sensors will not play very well until closed loop, and they wont prevent an engine from entering closed loop. Does your scanner do live data? If so what is the computer seeing for engine temp, and MAP readings? Your engine wont go into closed loop until about 170° to 180° and should run around 200° to 210°. If your map is pegged to around 30" of mercury even when the engine is running it's toast, it should be in the area of 7 or 8" when running at idle.
 

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2004 Avalanche. 2001 V6 Extended Cab ZQ8.
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Nothing looks crazy with those readings, but I do not know what normal is off the top of my head. A site like AllData or a GM service manual would have that information.
 

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Glowing cat is an indication of unburned fuel in the exhaust. Either the motor is over fueled or it is not burning the fuel correctly.

Is it misfiring on one particular cylinder?
 
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