I want to give Zack, aka
@zkdiesel, a HUGE shout out for his assistance last week. I had been fighting an issue with my Duramax and was striking out finding any valuable information on the interwebs. I sent Zack a PM with the question, and he instantly responded with his phone number to call. This pretty much goes back to our discussion a couple of weeks ago about having someone to bounce information off of when we come up against a wall. Well, I was up against a wall and to say I was getting frustrated with the keyboard warriors is an understatement. Over on the vehicle specific forum that I participate in once in a while, the specific DTC I was searching for had come up numerous times over the years but nothing addressing the actual data and how the ECM was interpreting that data. I thought there were some smart guys over there but unfortunately what I found was when a question was asked, it was the same mantra repeated over and over again, change this part or change that part. Any of us who've been wrenching long enough know that no two vehicles are the same and blanket statements are not always the resolution. Plus, I didn't want to simply swap parts or empty a parts cannon at my truck, I think those of you who follow me understand that's not me. No, I was seeking to understand the data. I thought I had a pretty good "bead" on various PID's before, but this issue had me stumped and I wasn't going to throw parts at the issue until I understood what the data was telling me. This is where I thought to reach out to someone who's skillset was obviously more advanced than my own and who's work I respect. I've never spoken to Zack before, nor really had any interaction with him other than some exchanges on this forum on various threads, so I wasn't sure how he'd respond to my question where he doesn't really know me either, but his selfless demeanor and knowledge on the subject were so very appreciated.
As we talked through the data that I had collected it was obvious that he has been in the diesel world much longer than I and his vast knowledge was so far above my own. Between his knowledge of the various PID's that I was mentioning and his willingness to help I could relate to his passion as well as understanding of the system(s).
Some preliminary testing I did prior to contacting Zack, when I thought I knew this system pretty well.
Without going into too many details about my specific issue, with the MAF reading skewed, I thought I possibly had an air leak after the MAF but before the turbo. So out came the smoke machine.
Nope, no issues there. Intake ducting and sealing was intact.
Then just to double check, I figured I would test the CAC and boost piping system. This didn't quite fit the symptoms, but it's an easy enough test and I always test these before doing any work as well as after a repair and I hadn't checked mine since my turbo rebuild two years ago so I figured I would at least rule it out as it's a free test and helps to check the integrity of the hot pipe all the way back to the cold pipe connection at the intake. This tested good as well, other than a very small leak at the backside of the EGR cooler. Without getting into details, let me just say I know with 100% certainty there is no way exhaust gasses through my EGR cooler can be excessive.
I did however, discover a leak at the backside when I pressurized the boost and ducting. I figured maybe I had an EGR valve that wasn't sealing well.
Off came the EGR valve and upper intake tract for inspection. Sure enough, there was quite a bit of carbon buildup, however, this had to be from the first 60k miles of its life vs. the last 70k but figured I'd give it a good cleaning regardless.
Pretty nasty and I figured it was possible the EGR valve was hanging open slightly, even though no exhaust gasses would pass through it.
Grabbed a few new gaskets from my local GM dealer for reassembly.
Intake valve and upper intake cleaned up and ready for reinstallation.
With everything in the system nice and clean and tight I turned back to the data and noticed there was no change. This is when I felt like I was up against a wall without any answers and when I thought I would shoot
@zkdiesel a private message and see if he'd be willing to shine some light on my dilemma.
In all this process I learned quite a lot, and I originally thought I had a pretty good idea of how the system worked. While I may have understood the system's functionality, I REALLY understand what the ECM sees throughout the process much, much better now thanks to Zack.
Goes to show no matter where we are in our specific fields, there is always something to be learned and it is especially nice when those who have said knowledge are willing to share it. Thanks again Zack.
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