Help! Lbz won’t run under 1200 rpm

[dmaxfireman]

Nah, that doesn't smooth out at higher rpm:woott:

Your woot woot face better be because you are starting your rock collection...

 

[juddski88]

Your woot woot face better be because you are starting your rock collection...

Hey man, if you have any rare ones to sell, I'm in the market.

 

[Unlimitedauto]

No news yet, but I did check the tps, and cam/crank sensors all ok. We’ll see...

 

[Unlimitedauto]

Alright guys the verdict is in....
CRACKED CRANKSHAFT!!!!

 

[zakkb787]

This was my first guess too. But being a bit of a newb to bottom ends, I never said anything

 

[juddski88]

Nah, that doesn't smooth out at higher rpm:woott:

Guess I'm eating crow tonight...seen several broken cranks but never one that ran better with more rpm. Thanks for the lesson!:thumb:

 

[JoshH]

So was the motor assembled with a broken crank? I thought the story was it was completely apart and never ran right after being rebuilt. I'm even more confused now.

I have also never seen one that runs better with more RPM.

 

[Cougar281]

So was the motor assembled with a broken crank? I thought the story was it was completely apart and never ran right after being rebuilt. I'm even more confused now.

I have also never seen one that runs better with more RPM.

I think the question is how 'completely disassembled'? Was it a shortblock and all the top end parts, or was it truly 'completely disassembled', meaning every part including the crank, cam, pistons, etc removed too. If it was a shortblock and top end parts, I could see how it could be missed on assembly in theory.

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[Jberger93]

Is the truck running better