I have a 1990 B2600i 4x4(120,000miles)that strated acting up last week. When I slowed down for a stop sign I noticed that the motor was idling extremely poorly (Around 500rpm). The truck runs great on the highway. It will kick down and pass at 55 without missing a beat. But when I slow down for a stop or to turn a sharp corner it starts sputtering. Upon inital startup after the vehicle has been sitting a couple of hours it is now stalling out. Expecially when I engage the automatic transmission. This drops the rpm well below 500. I remember is used to idle smoothly around 750. I have replace the plugs, wires, cap, rotor, fuel & air filters, and done a compression check. I'm thinking of a possible failing fuel pump, Idle speed control valve, or a BAC. Any info or advise would greatly be appreciated.
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