I have an 01 silverado with a 4.8l vortec 4x4. The thing that drives me crazy is my oil pressure gauge rapidly moves back and forth while idling. when i step on the gas there is some hesitation then is goes ok until i hit overdrive and then it feels like its skipping somewhat, the rpms go down then will come back up almost like its not getting enough fuel. this has been going on for a while now and heres what i have done. fuel pump, mass airflow sensor, knock sensors, intake gaskets, fuel filter, plugs and wires, fuel system cleaner. it has catalyst below efficiency threshold codes bank1 and 2. my cats are cut off with a flowmaster muffler. this problem was happening before i cut the cats. It seems like i have gone through everything fuel/air related i can think of besides coils,egr,injectors. could those be the problem? any help/suggestions would be greatly appreciated.

 

According to my Chilton manual the post cat oxygen sensors are not used by the pcm to control air/fuel. They are used only to monitor the efficiency of the cat.

I would suggest having the injectors cleaned. Also maybe try using a different brand of gas. There maybe something in your gas tank. Does it start OK? When you changed the plugs how did they look? Maybe a bad PCM.

 

Thanks for your reply when i did the knock sensors i cleaned the injectors and about once a month i run fuel injector cleaner in the gas. the truck starts perfectly fine. The plugs were pretty bad looking which i figured was due to the M.A.S being bad.