I have a 2000 Silverado z71. Just replaced transmission. Has 5.3 ltr engine in it. When i first start it up has no power and surges.after a few miles it runs like it should. If i need to go into a store same thing happens. I have aftermarket fuel pressure gauge, transmission and oil temp gauges on the Piller. When it surge's fuel pressure stays and the rpm gauge jumps around. Now about he transmission had it rebuilt with heavy duty clutches,vette valves, and towing converter are just a few things..
Long and short term runs normal as of O2 sensors. I have a torque app on my phone and a blue tooth adapter for computer...some times it reads the adapter and others it don't.
And some times it runs great from start. What are some things that i can look at to get it running right.
One of my suspicions is that computer might have lost some of its programming or its messing up.
Please help me any ideas will be useful.
Parts i replaced
Fuel pressure regulator
Complete tune up...wires,plugs,coils
Water temperature sensor.
Mass air and map sensor
Throttle body and sensor.
As i said before any help would be appreciated