This is nothing new to my 2005 4.8L Silverado. Usually the problem came and went but now it's staying. As soon as I crank my truck the electric fan cuts on and idles rough. As soon as I start to drive and apply throttle the temperature gauge goes from min to max (typically stays at 210) and the engine almost dies and cuts off, almost like it has bad gas. When I idle in drive the truck revs up and begins to speed up. Have big plans for the truck so I need help as to what to check or replace! Thank you!
First thing I would do is hook up a scanner and see what your engine coolant sensor is doing. If there is a short to ground, it would read over 300 degrees F. That would throw off your fuel mixture because the computer reacts to the temperature. Unplug the coolant temp sensor and see if the temp goes to -40F. that's what the open circuit should read. Plug it back in and see what the reading is. If it shoot all the way back up you probably have a bad sensor. If it reads normal, check the wiring to see is you might have a spot that is rubbed through somewhere and shorted to ground.
If you hook up a scanner and the temperature shows a good actual engine temp then look at your fuel trims and O2 sensor to see what they are doing when the truck is acting up