I have a 02 Escalade ext. I changed fuel pump, I changed fuel filter n chanded the fuel pressure regulator. And the truck still acting up. What is the problem

check thew fuel pressure regulator or the fuel pump may be weak

any check engine light on>?

have a fuel system pressure test done to check pump--regulator and filter. IF everything checks out replace the pressure sensor. Reset the light with a code reader

tank has to come out. Be sure to replace the complete FUEL PUMP MODULE. and the fuel filter.

SOUNDS LIKE TIMMING CHAIN REPLACEMENT NEEDED

Check your running fuel pump pressure. If (as I suspect) it's too low, first try changing your fuel filter. After changing the filter, recheck the running fuel pump pressure. If still low, check you fuel pump pressure regulator. If OK, you may need a new fuel pump.

Also probably would be a good idea to replace you air filter.

Good luck!

You need to establish and check your fuel pressure to make sure it's the same pressure it is whenever your car left the lot

Dirty fuel filter or faulty fuel pressure check valve which is located on your fuel pump sending unit. Try this test, turn the ignition on for 10 seconds (engine not running) then turn it off for 5 seconds and turn it on again then try to start the engine after 10 seconds. This will re-pressurize the fuel lines to start the engine, the fuel injectors need 62-65PSI to have them start the engine. Anything less then that and you'll have starting problem.
If it start's right up, then your ether have a fuel pressure check valve gone bad or a fuel leak at your fuel pressure regulator which is also common, but if your engine is still running 100% then i'll lean towards check valve or dirty fuel filter.

Start with the simple and replace the fuel filter, a dirty fuel filter will cause fuel restriction that may just be enough to the fuel pressure below 62PSI upon cold starts and a dirty fuel filter will cause the fuel pump to fail early in it's life.
Thank you for using Fixya and goos luck.

Get in the car and turn the key on, but do not start the engine. Do you hear the fuel pump running? After it runs for a few seconds, try to start the car. If it starts every time, then the symptoms you describe combined with the test indicate a failing fuel pump. Sometimes you can get codes from the cars computer which also provide some indication of what's failing. It could also be the fuel pressure regulator on the injector fuel rail

change he fuel pressure regulator