i guess fuel problems! need help!

[tripleD]

hey guys got the wifes 99 tahoe runs great and everything does great rite up until she pulls into traffic and hammers on it.than it starts dyin down,shaking ungodly and smells like eggs which would be bad cayts but just replaced them.you can pull over let it idle then go again.driving normal does perfect! its the 5.7 vortec.fuel pressure 55-58lbs. acts like its starving for fuel.anyone got any ideas!! i need eemm!! thanks

[G&R's57GMC]

Rotten egg smell says its going rich.

You'll need to get it scanned for trouble codes. Then Watch the live data for the O2 sensors, MAF, TP.

Another thing to watch is the fuel pressure while driving.

When did you last change the air & fuel filters ?

Have you ever changed the O2 sensors ahead of the cats ?

Be sure there are no air leaks from the MAF to the TB . If there is a leak it will cause the computer to use other sensors and a different fuel table. If the flex part of the tubing has a crack it may open when she gets on it and cause a leak.

[tripleD]

changed all filters.scanned for codes.hooked my pressure gauge up stuck it out on windshield and watched 55-58. done most everything im running out of options and patients cause if momma aint happy well u no the rest!!

[tripleD]

havent changed 02 sensors yet. tryin to weed out all the small things first.

[ChevyTech]

The fuel pressure is too low.

What pressure did you get with the, key on, engine off test.

How high does the pressure go when you crack the throttle with the engine idling.

[tripleD]

what is pressure supossed to be? key on engine off 58.crackin the throttle 53-55

[G&R's57GMC]

How many miles on the fuel pump ?

[tripleD]

not sure! i checked pressure on my 98 z71 verses the tahoe and it was bout the same and my truck will roll !!!

[speedygonzales]

KOEO pressure should stabilize to 60 - 66 psi. Under that is a problem.

I suggest checking the oil for fuel contamination. You can also check the #4 and #6 plugs to see if they are sooted more than the others. This could indicate the FPR has a hole in it.

Another indication is after the engine is shut down, the pressure will drop fast. So??? But don't be fooled by a fuel pump that has a bad check ball. They commonly go bad as well but when they do, it creates long cranking issues on start up.

The FPR is connected to the side of the central fuel injection connector UNDER the plastic intake plenum.

Also don't confuse an ignition issue with a fuel issue. For example, my Z71 will have a long cranking issue when the cap and rotor get too corroded. Incidently, I have found I need a cap and rotor every one to two years but can NEVER go longer than 2.

[ChevyTech]

Speedy gave you good information

The Key On Engine Off pressure should be 60-66PSI

The pressure should not go below 58PSI

When you crack the throttle the pressure should jump up, not go down.

[tripleD]

all that sounds gd but why is my z running so gd ? my pressure is 55-60 and its always been great even with nos on it! hers runs awesome up to about 55 t0 60 mph but pressure stays constant57-58 let out of it and it clears up in few min

[tripleD]

it cranks perfect everytime! changed maf sensor today and went and drove it for awile done great than i hammered down on it got it up to 90 mph and didnt do to bad! she will drive it tomorrow i will know than!! you would never know anything was wrong with it until you hold it in the floor!

[ChevyTech]

So many people think there vehicle runs just fine when they have a restricted fuel filter or low fuel pressure until it is repaired and then they are amazed at how much more power it has after the repair.

The computer will do its best to compensate for low fuel pressure and adjust the injector pulse.

Your vehicles could be doing a very good job of compensating for low fuel pressure because they don't have many other problems.

You may want to test your gauge on a few other vehicle to make sure the fuel pressure gauge you are testing with is accurate.

[tripleD]

thanks guys for the info! im still checking but its doin ok rite now! i will stay in touch and let you know the outcome!