2015 suburban 5.3l Rough Idle

[Taylor Paulson]

So short story is we moved from oregon to South Carolina we towed our 21ft camper took 8 days. Three weeks after we moved wife’s filled up car on regular gas. She noticed a rough idle and she was right. The following week I changed spark plugs and wires plus fuel treatment. Nothing made a difference it sits at 500rpms but will dip like 480ish and jump to 530ish at idle. I check throttle body little clean up done on it. Also spark plug on cylinder one was dark black and loose in there I undid it with my hand was barely on there. I put the new one in and the following I checked it and it was black black again. The weird thing no codes are popping up! Any insight will help! Expecting third kid any min so trying to fix this issue asap!

[CamGTP]

If it's just black that could likely be lots of extra fuel being sent into that cylinder. It's fairly common to have injector issues on these trucks.

 

If you had a nicer scan tool you could watch the fuel trims for bank 1 (drivers side), if that bank is showing lots of negative fuel trims it means there is lots of extra fuel on that side. The trims won't tell you what cylinder but the spark plugs will.