I wanted to post a thread regarding my personal findings on the whole chuggle/studder issues with the 15/16 Colorados.
As many of you, I also experienced severe chuggle at low RPMs with my 2016 Colorado Z71 Crew cab.
The first thing I tried was the Trifecta tune. As many of you reported on this forum, the chuggle eventually found it's way back. Then, here it came the famous Pedal Commander. While it severely reduced my pedal lag, at low RPMs, there it was the chuggle. The commander helped get rid of it by downshifting with less foot movement. The studder still annoyed me however. After the PC, I purchased the Diablosport Intune. I tried several settings there, nothing helped since after a while, the truck returned to it's old habits. Then, since I had the tuner already, I got with Jerry from BNR. He provided me with a custom tune and even changed raised the mph setting where the truck would upshift to reduce the chuggle. The custom tune helped a lot but the chuggle had a great comeback again.
You wonder why I am writing up all this boring stuff... Well, I think we all were looking at the wrong responsible party for the chuggle here. All the above tunes/mods helped greatly but the only thing that got 100% rid of my chuggle was switching to high octane fuel. I used 87 for all above experiments. I know, many of you stated on the forums that it absolutely should have nothing to do with the transmission performance, however, from my experience I believe that the ECM is "making" the truck chuggle. Let me explain.
As in the article I found on the BNR website (http://store.badnewsracing.net/Which...atter_b_1.html
), newer GM engines have an interesting self defense system, where they pull timings to prevent engine knock and/or detonation. Low octane gas is more susceptible to than high octane, especially in warm weather ( I live in FL). I personaly believe that the "TCM relearn" we experienced with the tunes is actually the ECM adjusting to the fuel after the programming. Some trucks may have a more aggressive adjustment to the point that it makes the engine chuggle at lor RMPs.
I have no idea why some Colorado owners don't experience the same chuggle but I bet that the RPMs at upshift are the same for the non chuggling truck vs the chuggling trucks. The variation in ECM adjustment to gasoline type might be different for some of us to the point where 87 does not produce enough power to keep the engine smooth at low RPM but 93 does. I am the living experience with some others on this forum that reported no chuggle with high octane.
In conclusion, on some trucks with the famous chuggle, you either need a tune that will keep the gears much longer before upshift (BNR has it) to prevent low RPMs with 87 octate or switch to 91 or 93 and enjoy a chuggle free experience. Please note that it took me two fillups with high octane to completely eliminate the issue.
Let me know what you guys think, enjoy your day!