1999 4.8 4x4 A real head scratcher!!! HELP

[borninabarn]

This vehicle acts like it is starving for fuel in small serges for the first minute or so after start-up. It then comes out of it and runs like a top. I have to wait approximately 1 hour and then restart the vehicle and drive it and again it will act up for around 1 min. I have had a fuel pressure guage taped to the windshield and it doesn't fluxuate at all. There are no misfires or codes and I seem to always have good spark and fuel pressure. This has been going on for about 1 year and getting worse all the time. I wish something would fail so I could replace it.Hope you techs out there have promising answer for this one. thanks born

[2000CAYukon]

Originally Posted by borninabarn

This vehicle acts like it is starving for fuel in small serges for the first minute or so after start-up. It then comes out of it and runs like a top. I have to wait approximately 1 hour and then restart the vehicle and drive it and again it will act up for around 1 min. I have had a fuel pressure guage taped to the windshield and it doesn't fluxuate at all. There are no misfires or codes and I seem to always have good spark and fuel pressure. This has been going on for about 1 year and getting worse all the time. I wish something would fail so I could replace it.Hope you techs out there have promising answer for this one. thanks born

Since you have a fuel pressure gauge, watch the pressure AFTER you turn off the engine. It should drop a little but it should hold pressure. If it drops to near zero, you could have a bad fuel pressure regulator (my guess this is your problem) or a injector that is leaking.

//2000CAYukon

[intel_guy]

I have a 99 4.8 4x4 that was having the exact same behavior (I had also posted here). At first startup I would step on the gas and nothing. Then I would REALLY step on the gas and after some 2-5 seconds hesitation, vroom, of I go. It also seemed to be worse if it was or had recently been raining. The main difference between your problem and mine, though, is that my truck was throwing misfire (P0171) code. My solution that has worked so far (~4 months) was new plugs/wires.

[borninabarn]

This sure does seem like a fuel related problem.One more thing the fuel gauge is erratic the fuel sender is bad im sure the customer goes by the trip odometer for fuel.would the fuel sending unit somehow be sending badsignals to the ecm?Also all data says the fuel pressure is supposed to be 42 psi shoud it be more?Let me know if you can think of anything!Thanks again born