98 Yukon bogs down

[cchrrice]

I recently purchased a 98 yukon slt with the 5.7 vortec engine. The previous owner told me that recently he had noticed that on two different occasions the vehicle just bogged down when the fuel guage was below 1/4 of a tank the first time he would take off, but then not again. I now have had that occur a couple of times exactly as he said. Recently it occured with half a tank and it did it more than once the same day. When you first accelerate it acts like it is starving for fuel, and if you back off the accelerator it will go. You then have to feather the accelerator to get up to speed and then it is fine. Anyone have any ideas before I change things that don't need to be changed. Thanks.

[94 Jimmy]

Fuel Filter? Fuel Pump? O2 Sensors? Tune-up?

It sounds like you are having an intermittent fuel pressure problem. If fuel pressure drops just a little (2-3 PSI) below minimum, the injectors can't stay on long enough to deliver enough fuel for the air being delivered by the throttle body.

Change the fuel filter, that's easy. If that dosen't do it, than have the fuel pressure checked if it's even a little bit low change the pump.

Also check the O2 sensors, if you haven't changed them in the last 50,000 miles just change them. If the O2 sensors are bad and giving a rich reading to the computer it will command the injectors to lean out the mixture and you get the same symptoms.

Also a general tune up is a good idea. If a plug is misfiring it will dump unburned fuel into the exhaust which will drive the O2 sensor rich etc., etc., etc.

Let us know what you fine, good luck.
94

[obadran]

I have a 96 Yukon, same engine, similar problem. It was fixed with a new fuel pressure regulator. With the ignition on, but not running, the fuel pressure should be in the 60's psi range....mine was in the low 50's....just enough to make the engine hestitate on accelaration.
Also, if I kept my foot on the pedal and forced the hestitation to last for a long enough period, the MIL light would come one....the fault code was both Bank 1 O2 sensors detecting Lean mixture.
Start with the simple/cheap fixes like what 94Jimmy suggested.