2004 Gmc Yukon - Loss Of Power And Very Rough Running

[Cadcom]

I'll try to make this a short story...

I had to replace the rear knock sensor on my 2004 Yukon XL w/ 5.3 Ltr. - again. Money is tight so since I just replaced the sensor about a year ago I decided not to replace the intake manifold gaskets. As soon as the sensor was replaced and intake buttoned back up I took it for a short test drive. It ran great. I decided to drive it to work the next day, ran great until about 25 miles of Atlanta traffic. Then check engine light came on and started to flash. Truck lost a lot of power and I had to throw it in neutral whenever I came to a stop or the motor would die. It idles very rough and had to shift down into first gear to climb a slight grade coming home that it used to not even drop our of overdrive for. Today I replaced the intake manifold gaskets thinking that would solve the issue. No luck and no change in the performance or rough idle. The local national auto parts place has a new code reader that they do not know how to read and couldnt figure it out. They said it was either telling them I need a new coil or injector or O2 sensor but they couldn't tell me which one. Truck has about 125k miles on it. Never changed plugs or wires and noticed the wires look a little rough. May do that tomorrow. I would be grateful for any assistance or ideas offered. Thanks!

[8.1HD/ALLISON]

Find somewhere and get the code read first. Unless you wanna waste money throwing parts at it. I would double check all the wiring connectors to your coil packs and injectors. Make sure there isn't a pin bent over or one thats not fully connected.