Possible fuel issue?

[holdenon12]

Hi everyone, I'm a bit mind boggled at the moment, so here's the issue. When I get out into the 100km zone and put my foot down the car slugs right out just struggles,you then take your foot of the gas let things settle then put your foot to the floor and it comes right. I have replaced the fuel filter about 3000 kms ago don't usually let the fuel go below quarter. I replaced my air filter yesterday for the first time.
Also I should add that it only does it in gear four. It is a 5 speed the 5L40E trans.
Any ideas would be much appreciated thankyou

 

[Fu Manchu]

The only way you’ll be able to answer what’s going on is with a high end scan tool to see what various systems data is restricting the performance.
Interpreting that data will take a degree of skill.

Cheapest semi decent scan tools like Vident or Topdon will be $350-$500.

To find the solution yourself, throw dollars and parts at it based on guesses.

A solid start is basic servicing.

1. Clean earths across all points on the harness.
2. Oil change.
3. Replace intake gaskets and torque intake plenum at 23Nm.
4. Smoke test intake to find even the smallest vacuum leaks with visual conformation.
5. Service the trans (the 5L40e is $$$ to rebuild. Love it. Care for it.)
6. Run some injector cleaner through the system.
7. Visually inspect and feel the connecting hoses to the intake. Replace hard hoses.
8. Plan to replace O2’s as a service item. 2 wide band. 2 narrow band. Only use Bosch.
9. Remove the manifold guards and inspect manifolds for cracks.
10. Get a battery health check done and have the charge system tested.

11. Get a decent scan tool