Duramax Knocking

I have an 05 duramax, has 80,000 miles on it. I also run an edge tuner. My last two pulls to the racetrack, I have noticed some knocking. Tonight coming home it as worst as I have ever heard it.. I seems to only occur between 1400-1800 rpms when I am doing a slow pull away from a stop with the trailer. Now if I pull away from being aggressive with the throttle I don't hear it. It has been awhile since I put a fuel filter on it so I was going to do that, also I usually run total power in the truck but i ran out a couple of months ago, so I am wondering if that could have something to do with it. So do I need to get it to a shop?

Thanks in advance.

With a diesel, assume any knocking sound is injector related till that possibility has been eliminated. The eight individual injectors can be disabled one at a time using a scan tool. If the sound goes away or becomes a lot less noticeable when disabled, you've narrowed it down.

Jim

So when an injector goes bad, is it typical to be intermittant? Or do you hear it all the time. The only time I have heard it is after a long pull. I took it into a shop, hopefully I will get good news tomorrow.

After a long pull (tough duty), the fuel is thin (hot), and the internal tolerances of the fuel system components are at maximum. So yes, it can be intermittent. "Intermittent" is more of an indicator of a fuel system/injector issue.

Well buddy's shop found two things, but since they don't specialize in diesel they are getting a second opinion from from a second shop. First he said that it looks like the egt system is completely clogged up. Also he said it looks like the internal seal on the turbo is leaking oil. Before anyone says anything, the guy that owns the shop is a very good friend of mine so they want to make sure what they recommend will fix the issue.

So would either of these issues cause an intermittent knock?

I replaced the head gaskets on my '05 a couple months ago. The EGR system and thusly the intake manifold and head was gooey, but not clogged (but I still want to either block the EGR system or have Kennedy do the magic on the ECM to kill it). I wonder if the tuner is causing excessive soot or if the leaky seal is making the exhaust extra gooey and causing the clogging. Dunno if the air restriction would cause knocking or not, but IMHO it is worth the dough to kill the EGR system.

Oil in the intake is not abnormal. The crankcase vents into the intake. Continuous high-power demands can cause a higher level of oil vapor to pass through the plumbing. This can collect in the turbo, CAC and lower plumbing, and coat everything in between. The turbo oil seals rarely fail before the turbo itself gives up. The oil channel is only pressurized to the bearing cartridge, then gravity drain (no pressure) to the crankcase. This/these conditions won't cause a knock, but either condition, if excessive, can cause a run-on until the oil supply stops. To a Diesel engine, engine oil is just another fuel.

The "goo" in the intake plenum and heads is cause by a combination of exhaust gas/soot (EGR) and crankcase vent oil vapor. Stopping one of these will leave much less of a mess.

Being a LLY and intermittent knock I'd be suspicious of teh #2 and #7 injector connector issues.

I doubt that you have a turbo seal issue.

Do the harness issue typically trip a code? I took a good look at them and didn't see anything obvious.