I have an 89 ford ranger with a 2.9 v6. replaced the fuel pump yesterday and when I started it on a cold start the truck ran perfect. after the truck started to warm up a bit and I started down the road to test drive it, it would run 2000 rpms fine but anymore than that it would sputter out. after bringing back to the shop and letting it sit and idle, you could give it any gas without it sputtering out. found one vacuum leak but didn't seam to solve the problem. any advice would be greatly appreciated.

 

Welcome to the forum.

Why did you replace fuel pump?

Can you get a pressure gauge to test fuel pressure?
1989 EFI should be 30-40psi running, and hold above 20psi after being shut off for 30-60minutes

Revving engine in drive way isn't the same as when under load on the road
Fuel consumption is more than doubled when engine is actually pushing vehicle weight down the road.

You can mimic a bit of a load if you have it in gear foot on the brake and give it some gas.
Be careful

On the fuel rail(engine) is the FPR(fuel pressure regulator), the Return Fuel Line is attached to it.
It has a spring inside that holds the valve closed if pressure is under 30psi.

You can remove the Return fuel line, there will be some fuel coming out so have a towel or ?? to catch it.
Then turn key on, DO NOT START ENGINE!!!
Fuel pump will run for 2 seconds
See if fuel comes out, it shouldn't

Thinking FPR is leaking or stuck open, bad spring, so pressure is low

Other thing is the fuel filter, was it changed as well?
Dirty filter, or screen/sock in the tank, allows some fuel to flow but as demand increases fuel pressure goes down from limited flow and engine starves for fuel

 

I replaced the fuel pump because it didn't have adiquet enough pressure to it, also changed fuel filter, and egr. haven't checked the pressure since I changed the fuel pump but not sure of the fuel is my problem. has one vacuum leak that I have found but still doesn't run right if you clog the hole. it doesn't matter if it's under a load or not, once the truck warms up, you has the same reactions wether your going down the road or sitting still. it sputters out over 2000 rpms but idles fine

 

What happened to "you could give it any gas without it sputtering out"

If you can retest pressure then I would.

Running OK cold but not warmed up is a classic sign of TFI module or coil starting to fail.

Good read here on TFI system: Ford EEC-IV/TFI-IV Electronic Engine Control Troubleshooting