04 Cummins problem, intermittent knock

DDually

DDually

Still spooling..
Joined
Nov 30, 2009
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I have a weird problem on a friend's 04 auto truck with 170k miles.

It has a noticeable knock when driving and rolling. It doesn't knock at all when it's sitting there idling in park, drive, reverse, or nuetral. It doesn't smoke at all, it has no notable blow by, and the oil pressure is good according to my mechanical gauge. I was thinking about pulling the valve train off to see if there is anything weird going on in there. Another thing to note is that it is matched with engine speed, not vehicle speed. It idles really smooth too, it doesn't feel like it's running on 5-1/2 cylinders or anything.

I was thinking maybe a cracked flex plate.

Is there anything else that would making a rod knock type sound?

Is it worth check compression if there isn't bad blow by?

Is it worth having the injectors sent off to be checked if it doesn't even haze at idle or cold start?

This is kind of a beat to crap ranch truck and it's been used and abused.

Short story: knocks when moving, no smoke, no blow by, doesn't knock when idling or sitting in drive.

Thanks,

Jared
 
I would check rail pressure and look for a spike when it starts the knocking. Could be a sticky FCA if thats the case.

May run a dose of Diesel Kleen through it as well, I have seen that fix similar problems.
 
Last edited:
SPEEDSHIFT said:
I would check rail pressure and look for a spike when it starts the knocking. Could be a sticky FCA if thats the case.

May run a dose of Diesel Kleen through it as well, I have seen that fix similar problems.
Click to expand...

Will do. Ill try both.
 
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