Engine Performance problem
1988 Chevy Truck 6 cyl Two Wheel Drive Automatic 235K miles
1988 Chevy 1500, 4.3L, 375 Transmission (3 speed auto), 235K miles
Father, brother and I are all decent mechanics/parts changers, but this truck has us stumped.
It hesitates during acceleration whenever engine is under any stress. Less noticeable after closed loop. Significant lack of power below 2000 RPM. At take-off, while still in open loop, hesitation is huge, but disappears when I flutter the gas. This also usually results in what I would consider normal power for motor and truck size. Take-off on slight downhill also seems to be more like normal, and more than caused simply by the slight downhill.
Have had this truck 10 years. Installed ACDelco long block at 165K miles, rebuilt tran at 220K, have replaced every sensor, valve, controller, etc. at least once, replaced distributor, rebuilt throttle body. Had it in shop at one time, they claim to have replaced computer. Installed Schrader valve, fuel pressure at rear of TBI held consistently at 11 PSI while driving, even uphill. TPS and MAP sensor voltages read appropriately, even while driving. Some of these changes have improved overall performance, but none has affected this particular issue. Any suggestions?
1988 Chevy Truck 6 cyl Two Wheel Drive Automatic 235K miles
1988 Chevy 1500, 4.3L, 375 Transmission (3 speed auto), 235K miles
Father, brother and I are all decent mechanics/parts changers, but this truck has us stumped.
It hesitates during acceleration whenever engine is under any stress. Less noticeable after closed loop. Significant lack of power below 2000 RPM. At take-off, while still in open loop, hesitation is huge, but disappears when I flutter the gas. This also usually results in what I would consider normal power for motor and truck size. Take-off on slight downhill also seems to be more like normal, and more than caused simply by the slight downhill.
Have had this truck 10 years. Installed ACDelco long block at 165K miles, rebuilt tran at 220K, have replaced every sensor, valve, controller, etc. at least once, replaced distributor, rebuilt throttle body. Had it in shop at one time, they claim to have replaced computer. Installed Schrader valve, fuel pressure at rear of TBI held consistently at 11 PSI while driving, even uphill. TPS and MAP sensor voltages read appropriately, even while driving. Some of these changes have improved overall performance, but none has affected this particular issue. Any suggestions?
Jun 5, 2009 at 8:59 PM
