97 Tahoe 5.7 hard starting high idle

[Ryan cin]

Truck starts right up when cold but idles at 1000. After I shut it off and try to restart, it doesn’t start unless I fully depress the gas pedal and slowly let up.


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[b454rat]

Idling high kinda sounds like vacuum leak....

 

[PlayingWithTBI]

Idling high kinda sounds like vacuum leak....

^^^X2

Check your fuel pressure and, if it bleeds down after you turn off the key too.

 

[east302]

After I shut it off and try to restart, it doesn’t start unless I fully depress the gas pedal and slowly let up.


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X2 on the pressure test.

That’s the clear flood mode, holding the gas down while starting stops injector flow.

Fuel pressure spec for a vortec is 60-66 psi with key on, engine off. It should hold near that after turning the ignition off. If it bleeds down then it’s either leaking at the pump (check valve), at the regulator or an injector.

Is it throwing any codes?

On the vacuum side, there’s a hard vacuum line that goes from the PCV fitting across the intake to a solenoid on the firewall near the a/c accumulator. See if it’s still connected.

 

[SUBURBAN5]

X2 on the pressure test.

That’s the clear flood mode, holding the gas down while starting stops injector flow.

Fuel pressure spec for a vortec is 60-66 psi with key on, engine off. It should hold near that after turning the ignition off. If it bleeds down then it’s either leaking at the pump (check valve), at the regulator or an injector.

Is it throwing any codes?

On the vacuum side, there’s a hard vacuum line that goes from the PCV fitting across the intake to a solenoid on the firewall near the a/c accumulator. See if it’s still connected.

Mine at 50psi. What can I do to improve that. Been like that since new pump new injectors new filter. I thought maybe fuel regulator but it's not adjustable

 

[east302]

Mine at 50psi. What can I do to improve that. Been like that since new pump new injectors new filter. I thought maybe fuel regulator but it's not adjustable

It starts ok? No, the regulator is not adjustable.

Differentiating between the pump and regulator requires putting isolation valves in the supply and return lines at the filter. Not a huge ordeal, just a few tests with a pressure gauge and some creative arrangement of fittings from a hardware store.

I’ll toss in possible low voltage or a ground issue at the pump as well.

 

[SUBURBAN5]

It starts ok? No, the regulator is not adjustable.

Differentiating between the pump and regulator requires putting isolation valves in the supply and return lines at the filter. Not a huge ordeal, just a few tests with a pressure gauge and some creative arrangement of fittings from a hardware store.

I’ll toss in possible low voltage or a ground issue at the pump as well.

I'll look into it. I was thinking of getting an adjustable fuel regulator but if that's not a solutions then I dont mind putting a regulator at the return. Just dont know for sure what route

 

[east302]

Forgot to mention, if it’s starting fine then I’d wonder about the pressure gauge accuracy.

 

[Ryan cin]

Thanks for the replies. I’m pretty sure I don’t have any vacuum leaks, I checked with carb cleaner and a propane torch. I let the truck sit for 3 days and this problem started.

 

[Ryan cin]

Well a new problem made itself known today. Pulling out of the gas station my truck decided to shudder and stall right as I was starting to pull out into traffic. If I don’t let the truck idle for ~3 mins after starting even when it’s warm it stalls when I put it in gear. So my symptoms are:

-High idle
-Hard hot starting (have to fully depress pedal then mess with it a little)
-Stalling in gear

I don’t want to start randomly throwing sensors at it, so what would have the best chance of being my problem?