2004 LLY with an engine knock

Big Blue24

Big Blue24

Comp Diesel Sponsor
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Jan 5, 2008
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2004 Chevy Dmax with 140K miles with an engine knock. The check engine light is on, the RPM surges just a touch. The knock is louder on the passenger side, and seems to be louder on the under side of the motor.

From in the cab, it feels like there is a slight miss till about 1800 rpm. I'm not a Dmax mechanic but it seems like an injector issue to me.

What do you think the problem is?

[ame="http://www.youtube.com/watch?v=mTw4z8-t3HY"]http://www.youtube.com/watch?v=mTw4z8-t3HY[/ame]
 
Any smoke out the exhaust? Fuel dilution? Did you hook up a scanner? Thats an LB7 FYI
 
I think you have a rod slapping around in there. But I would do some monitoring on it and see what the ballance rates are.
 
JWhite said:
Any smoke out the exhaust? Fuel dilution? Did you hook up a scanner? Thats an LB7 FYI
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I honestly wasn't sure if it's an LB7 or LLY, the owner told me it's an 04'.

I'll have the codes later tonight. I recommended he take it down to Dmax doctor here in town, Under Ground Diesel Performance since I'm extremely limited in experience with the Duramax motor.
 
Big Blue24 said:
I honestly wasn't sure if it's an LB7 or LLY, the owner told me it's an 04'.

I'll have the codes later tonight. I recommended he take it down to Dmax doctor here in town, Under Ground Diesel Performance since I'm extremely limited in experience with the Duramax motor.
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It threw me for a spin, never actually seen an LB7 with egr before.

Whats the history of the engine? Generally a bad bearing doesnt sounds consistent like this truck does, could be overhead. Just run it till it blows, then you find out what was wrong :umno:
 
Big Blue24 said:
I honestly wasn't sure if it's an LB7 or LLY, the owner told me it's an 04'.

I'll have the codes later tonight. I recommended he take it down to Dmax doctor here in town, Under Ground Diesel Performance since I'm extremely limited in experience with the Duramax motor.
Click to expand...

Newly and Mike will be able to help him for sure.
 
Shut it down, doesn't sound like any injector knock I've heard.
 
yea that sounds more like a dropped valve or really loose overhead to me
 
Id check balance rates, If they came back good, Command full rail pressure at idle, that will eliminate anything in the CP3. If it still continues start taking the top end apart
 
My hell....that sounds like an old 6.2. I highly doubt that's an injector problem
 
LB7's had EGR on them from 2002 - 2004. They were sold in a total of 13 states with EGR the rest of them had no EGR. That sounds like the injectors are not firing correctly. Do a compression check first and see if the cylinders are low. If you have a bunch of them off my guess would be the cam pin has broken and the cam is out of time or one of the injector harness is shorting out and that causes them to run like that but the compression will check good.
 
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