Truck surges under partial load

JASON SEDGWICK

MEMBER
1996 CHEVROLET SUBURBAN
5.7L
V8
4WD
AUTOMATIC
138,000 MILES

My truck surges and bucks real hard when it is under part load. It starts and idles fine and accelerates great when the pedal is planted. It acts up when you are accelerating from a light or when its stalled up in the driveway. Also, I can only duplicated it surging in drive. When I stalled it up in the driveway in reverse, its fine. I have replaced the fuel filter, air filter, and fuel pump with no change. No check engine lights are on. No vacuum leaks that I can see. Engine was rebuilt by a shop when the previous owner had it. My thoughts are; fuel pressure regulator or spider injector assembly, but I can't afford to take that gamble just as a guess. Also can't really afford to take it to a shop to have them diagnose it.

1 Reply

AL514

MECHANIC
4,675 POSTS

Hello thanks for using 2CarPros. If you think its the spider fuel injection assembly, there is a pretty easy leak down test you can do without having to remove the intake plenum. Is basically a fuel pressure test but making sure the system holds pressure for at-least 5 minutes after the truck is turned off. Attach a fuel pressure gauge to the fuel rail, and cycle the key on and off a few times to get pressure up to its max and watch the gauge for any drop to 0 psi. If it drops to 0 psi right after cycling the key, then there is a leak somewhere in the system under the intake plenum. This is a pretty easy test. https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator