ok, ive searched here and all over the net and cant seem to find ANYONE who has or is having the same issue with similar symptoms. this is on my dads truck also, 2004 silverado with a 5.3

the other day he was headin home and as he pulled up to his shop the truck started running rough at idle. he says he smelled something amost as if it was a burning smell, or what im guessing was a "rich" smell. anyways, the truck started flashing the check engine light and is throwing 2 codes, p0300 random multiple cylinder miss fire and a p0171 system 2 lean on bank 1. it only runs rough at idle when you step on the skinny pedal it ***** and gets with no issues. we swapped the front 02's side to side to see if the code would follow and no luck. i understand that 04+ supposedly has no inline fuel filter and the regulator is in the tank. im still thinking it would be an 02 sensor but really dont wanna start guessing on $100 parts. thanks in advance

 

I can confirm the no inline fuel filter its in the tank. And generally the flashing check engine light happens when its throwing a misfire code and u run the engine past a certain RPM the light blinks meaning ur possibly harming the engine. My 04' had a similar problem once but mine happened to be a loose plug wire and then I had a misfire on cylinder 7 in which I had to pull the fuel rails and injectors to clean them.