I have a 1999 Chevy Silverado 4x4 with 64k miles, 5.3 L engine and
automatic tranny. The truck "stumbles" at different times. The
problem generally occurs when I first start the engine and put in gear.
Once I begin to give it more throttle, the problem starts to
dissipate. During acceleration at low rpm and slight throttle it also
stumbles/bucks. The truck seems low on power in overdrive but when it
kicks down, it seems to be ok. I have changes plugs and fuel filter.
No trouble codes or check engine light. The dealer was unable to find
anything wrong...it was working well when I took it in. Any Ideas? I
can recreate the problem by holding the brake and throttle, loading the
engine. Mostly this is noticed under 1500 rpm.