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I have a bone stock 05 LLY that I got about 2 months ago. Shortly after I bought it I had to replace 2 injectors. When they were diagnosed by the GM dealership here, they said that they had to do more than usual to diagnose them as bad. I replaced them and the truck runs a lot better but still not 100% right. There is a bit of clatter while cruising only under moderate to slight load. Also, there is a little smoke at any throttle that clears up when cruising but if you punch it the black smoke is very thick. I'm also hearing a weird chirping sound at around 1500-1700 rpm that I cant figure out. The typical exhaust whistle on idle due to the VGT is not there but the truck has stock exhaust. Any thoughts?
 

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I would check the air cleaner first then pull the air horn off the intake side of the turbo and give the turbo a wiggle. Most wiggle a tag but you will know it its bad. Might even change your oil, since you dont know much about the truck. That dirty oil lubricates the turbo as well. If you have access to a scanner tool that would do it I would check the balance rate on the injectors again.
 

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I have a bone stock 05 LLY that I got about 2 months ago. Shortly after I bought it I had to replace 2 injectors. When they were diagnosed by the GM dealership here, they said that they had to do more than usual to diagnose them as bad. I replaced them and the truck runs a lot better but still not 100% right. There is a bit of clatter while cruising only under moderate to slight load. Also, there is a little smoke at any throttle that clears up when cruising but if you punch it the black smoke is very thick. I'm also hearing a weird chirping sound at around 1500-1700 rpm that I cant figure out. The typical exhaust whistle on idle due to the VGT is not there but the truck has stock exhaust. Any thoughts?
I would say you either have a turbo issue or a sizable leak in your intake side. Still a lot of info missing to be accurate. Dean
 

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Discussion Starter #4
I would check the air cleaner first then pull the air horn off the intake side of the turbo and give the turbo a wiggle. Most wiggle a tag but you will know it its bad. Might even change your oil, since you dont know much about the truck. That dirty oil lubricates the turbo as well. If you have access to a scanner tool that would do it I would check the balance rate on the injectors again.
Air cleaner is brand new. I’ll check the play in the turbo shaft. I’m taking it to the dealership tomorrow for the overfueling issue and mention a possible boost leak.
 

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Discussion Starter #5
Update:
Bailed my truck out of the dealership. It was diagnosed with a bad injector (#6). It went unnoticed until I changed 1 and 8. I'm guessing that this will turn into a "replace all 8" job. As for the chirping sound I am almost 100% sure it isn't the turbo. The dealership told me that it made proper boost and no boost leaks. They also took off the turbo inlet and wiggled the shaft. Fine. Also, I can hear the turbo spooling up and the noise concurrently, leading me to believe that it isn't coming from the same place. I thought it may be a pulley so I listened to it under the hood. I'm now pretty sure that it is a chassis vibration.
 
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