My friends '03 duramax has developed a studdering issue in the last couple days. It does it continuously while idling or driving down the road. Under light throttle or accelerting. He said he just changed oil and fuel filters about 150 miles back, so fuel filter shouldn't be an issue. Also when standing outside the truck, u can hear a pretty loud tapping sound. But not like a rod knocking cause it isn't continuous, no rythme to it. The truck has just over 100K on the ticker of some pretty hard miles as a farm truck. He just had new injectors changed a couple months back, they were leaking into the oil. My first thought were that maybe something related to the injector change may have backed off or came loose causing the studdering and loud tapping under the hood. We are currently on a job and can't get it into a shop for a few days so any thoughts or suggestions are welcome, thanks.

 

could be injectors again, does it sound like loose valves or does it make a tack tack tack noise on the outside.

if he can find some one who can check his balance rates. does his rpm jump up and down too at idle?

 

The sound is more of a tack tack tack, just not consistent. Don't recall about the rpm, I just went out and fired it up, but it was not doing it with a cold motor. Maybe at operating temp. I will see if he is going to drive it this afternoon when he gets off work.