Ben1029

Found and fixed issue PCV line fitting was cracked on intake causing stumbling idle and stalling. Brought truck to dealer and told them to keep truck until fixed and got rental car for 4 1/2 weeks just for a PCV line. No issues now for 3 full weeks.

I have a 2020 sierra 1500 SLT and mine has same issue. This is going to sound stupid but this fixed my issue. Been into dealer 3 times and the last time it was there they replaced the PCV line hose and ever since then it has not happened. They found a cracked fitting on PCV hose and would only shake or stumble at idle. I would recommend changing PCV line

No codes, no pending codes and no lights on

I did look at plugs and none are cracked as I can see

I do have a solus plus scan tool I use but it’s hard to figure out what’s going on be I only have limited time from when it happens. I do know when GMC removed my intake for warranty work they pinched #2 ignition coil wires and taped them up because they said they were still connected. but I still have no misfires on any cylinders. I’m wondering now if the #2 coil wires that were pinched are causing issue even though it may not be a big enough misfire to detect?

The plugs were bought at GMC with OEM plugs and I installed them . I will inspect plugs but if the ceramic on plug is cracked it more would have misfire under load. Not saying it can’t happen at idle but it would happen more under strain or load on engine

Yes, this truck has been to dealer 3 times and they say it’s normal. There are no codes or anything in system. We cleaned MAF sensor, replaced all filters and even throttle body cleaned but issue still happens randomly

When it’s cold outside (20 degrees or colder) the truck starts and idles normally, but once engine temp gets to normal temp then I come to a stop or slow down below 5mph the rpm’s surge/ or change and sometimes stall out. Once it stalls you hear a pop noise. I can raise rpm’s then it goes away but it will come back again. Truck has been to dealer 2 times already and they say it normal but I don’t think so. Not sure what to do because it’s getting annoying -changed spark plugs at 48,000 miles -transmission fluid was changed 45,000 - new air and cabin filter - run 89 octane fuel

No luck, we removed rear seats and still rattles on front A-pillar area

2020 gmc sierra SLT 5.3l 10speed when driving at highway speed 65mph or higher it’s sound like marbles being shaken in a glass jar. We removed A pillar trim on passenger side, upper and lower glove box, cabin air filter, passenger speaker and cover, passenger fuse panel cover, center vent cover by window and removed radio antenna. We tightened down cab mounting bolts to spec, tightened running boards, tightened wiper mounting transmission assembly, replaced 3 plastic tree clips and taped them, tightened blower housing bolts and tightened passenger Side mirror and noise is still their. Need some assistance to help find noise because I’m not paying $209hr for someone to look at my truck. Thanks

2020 gmc sierra 1500 SLT I have rattle noise like marbles in jar being shaken at highway speeds (65+) in passenger side A-Pilar area. We removed pillar cover, replaced plastics push pins with new and taped them down, removed passenger front dash speaker, tightened both running board bolts, loosened and tightened body mounting bolts, remove antenna, removed passenger gloveboxes, removed cabin filter and removed passenger seat belt with bolts and still makes noise. I’m stumped and need assistance please. thansk