I have a 09 gmc 1500 truck with a 5.3that started off with a high idle would go up around 3000rpm. Took it to a ship scan read misfire on cylinder 4. He changed the coil pack then it read map sensor problem. He unplugged it and then plugged it back it along with the mass airflow sensor. Now it idles so rough it will hardly stay running. And the fast you drive it the worse it gets. Please note this truck recently had a cam job done by a professional along with new plugs and wires any ideas?
I would venture to say there is an issue with the AFM system in that motor. Wonder if the new cam used was an AFM cam which it needs to be.
Good point I bought the truck used so I don’t know the background of it but I’ll definitely ask some questions thanks
Well to begin with it sounds like idiots are working on a vehicle just plugging stuff in and unplugging and plug and stuff back in that's no real test of anything. You need to find a guy like me who has a very fancy scan tool and knows how to operate it to do bi-directional testing and analysis of the data. Anyone who just unplugs and plug stuff in is not a real mechanic these days they are much more complex than that to analyze
I’ll be looking for a new mechanic but they are hard to come by where I live. I sure wish I was closer to you thanks for the comment