QuestionI have a 97 Chevy z71 5.7 4x4 with 140000 miles on it. I dont drive it everyday like I use too and recenttly started to have problems with it, that it starts up and idles fine but when you go to get on the gas to accelerate it starts to kill itself less you back off the thottle. I have replace the feul pump, fuel filter and tested the fuel pressure at the rail, Installed a new fuel pressure regulator at the same time as the intake gaskets. plugs wires and cap are new, coil is new, The oxygen sensors zero out on the computer when it acts up, I ve replaced the cats. I have unplug the Egr Valve and Maps Sensor to see how they affect it and no luck. I am down to the computer or ignition but those get a little spendy, there is no affect when you drive and shift up thru the gears as well. Have I stump you yet? any Ideal on where to go from hear?
AnswerHello Charlie,
I hope you got the correct fuel pressure. 13 PSI for throttle body injection, and I believe about 45 PSI for MPFI systems.
If not, there is a hose in the tank that connects the pump to the tank unit. I have seen them split, and only maintain part of the needed pressure, the rest spraying out inside the tank.
If your pressure was up to spec, then I would connect the tester, and see what it does when the engine sputters and dies. The fuel pressure should stay up there till after it dies.
If so, then I would check the TPS.(throttle position sensor). It could be giving an incorrect signal, or no signal, and when you open the throttle plate, which is mechanical, you dump in a bunch of air, and the fuel is still at idle, or limp-in default.
Older models even had a "clear flood" mode, which at wide open throttle would stop injecting fuel, but that may have only happened during cranking.
But the TPS is where I think you might look.
Electrical connections as well.
And before replacing it, the TPS is testable with an ohm meter.
Van
