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casey.mikl

2011 2500hd 6.0 misfire

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I have a 2011 Chevy 2500hd with 6.0. The truck has developed a misfire at idle and partially on the gas. I have replaced all the spark plugs, all 8 injectors, moved coil packs around, replaced MAF, MAP, b1s1 02 sensor (was getting codes for that sensor only), ECU, fresh gas and added cleaners, cleaned throttle body and swapped throttle body, had cats removed (already were blown out and empty) Nothing has solved the issue. Only bank 1 is misfiring. Mainly cyl 1 and 3. The truck backfires out the exhaust, and under load back fires out the intake. It will clear up like a switch flipped and run fine until the truck is shut off and restarted. I’m at a complete loss. By watching the snap on scanner. It appears as if it’s richen bank 1 and lean bank 2. I’m at a complete loss. It’s happening at idle and slightly off idle until it decides to clear up. I have been getting codes for random misfire and bank 1 sensor 1 02 sensor for heater issue.

 

 

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I was thinking possibly crank sensor or cam sensor but what doesn’t make sense to me is that it is only misfiring on bank 1 and not bank 2. And that it is fattening up bank 1 and lean out bank 2. Atleast the pulse width for the injectors is showing off on each bank. When it runs fine they are equal. If not they are off by a lot. Like 3.5-4.0 and 1.5-2.0


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?,that backfiring in intake,leads me towards crank sensor,one test is watch rpms on scanner and spray cool water on crank sensor,see if it changes anything, another is,move wiring a little for crank sensor,anywhere it's accessable,and safely

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I’ll have to try the spray on the sensor as that seems a little easier and safer. It will backfire through the intake under load. No load at idle it back fires out the tail pipe.


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I haven’t done the test with the water. I had a spark plug that burned out (it had maybe 1500 miles on it) and I had to order a new set of plug wires for it. I’m gonna replace the plug and put new wires in it. I’m going to replace both up stream 02 sensors as well with new bungs. The threads on bank 1 are messed up and the sensor doesn’t seat fully into the pipe.


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I replaced the bad spark plug today, along with all of the wires, the body to motor ground, and cleaned the main engine ground. I did notice that the wiring inside of the loom is rather brittle and corroded. I will be replacing the main ground from the battery to the engine. Here are some of the graphs that the scanner is showing. What I’m noticing is that bank 1 (side that always misfiring) 01 sensor number 1 is not nearly as “sensitive” as bank 2 sensor 1. Also fuel trims between the 2 sides seem to be off as well. a5a49ab3afb2c2af925c506bd6eab045.jpg
b865138b46f043bf9a42caa7144305de.jpg
87b28d13fc12c1ecab76a7b95ab582f1.jpg


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Okay. Little update if any one is able to help. I replaced the ground cable that was corroded. I checked for power and ground at all the sensors. When I use the sensor grounds, I get 8.70 volts with key on engine off. If I use the sensor positive and the ground of the motor, I get 12 volts. Where do the o2 sensors ground to? I have replaced the factory ground to the battery as well as firewall to rear head ground. Still no luck


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