Hesitation on initial start up

[Marcos Beltran]

I have a 96 GMC with the 4.3 V6 motor. When starting the truck it will hesitate the first 2 or 3 times of pushing the gas pedal. After that it works just fine. This will only happen if the trucks been sitting over night or for a few hrs. If i shut the truck off and start it up it wont dont do it again. Ive done quite a bit to this truck and have no idea what could be causing this. Was having the P0171 and P0174 CODES but got those corrected. Not showing any codes now. Any ideas anyone?

 

[stutaeng]

Leaking fuel pressure regulator (FPR) and/or injectors leaking overnight. Have any of those been replaced? Also check for fuel pressure.

What was the cause of the P0171/P0174?

 

[Marcos Beltran]

Leaking fuel pressure regulator (FPR) and/or injectors leaking overnight. Have any of those been replaced? Also check for fuel pressure.

What was the cause of the P0171/P0174?

Injectors and regulator are original to truck i assume. The fuel pressure is within specs, checked it when the fuel pump was replaced. It was a vacuum leak at the throttle body seal that was causing the codes.

 

[Schurkey]

Verify fuel pressure, specifically rate of loss of pressure when the pump quits running.

Connect a scan tool, look at the data stream, especially when in open-loop.