I just dropped of my Colorado at the dealer.. I've noticed the last few hundred miles I was getting a loud pinging/rattle metallic sound that I kept thinking was a headshield. I checked every inch of all the heatshields and they were all tight. Its gotten so loud that I can hear it over the radio now. I put in premium gas 93 and within the first 30min of driving with primum the rattle sound disappeared. Also I've noticed my gas mileage has gone up 6-7 mpg since adding primum. I found a bulletin about a ECM TCM update so I printed it out for the dealership. Unfortunately its out of warranty now. Has anyone here had the same problem and has the ECM update fixed your issue?
So I picked up my truck and they did a PIP5303 update on the ECM/TCM. One the issues noted on that bulletin was spark knock. Once driving off the lot I couldn't believe how different the truck responds now. It is so much more responsive and has so much more pick up. When entering the highway from the onramp I used to have to really step on the gas or It was like it was stuck into low of a gear I just assumed that was normal I guess. I still have primum in there now so I wont know if this fixed the engine ping/spark knock until my next fill up.
Although the truck is driving so much better. I just filled up with 87 and the spark knock/engine ping came right back. Anything I can try before bringing it back to the dealer? It’s out of warranty and it’s going to cost me a fortune I can imagine. I put my scanner on and no codes or stored codes.