S10/T10 P/U 4WD V6-4.3L VIN X (1996)
PROM - Programmable Read Only Memory: All Technical Service Bulletins
Engine - High Idle/Flare when Shifting Gears
File In Section: 6E - Engine Fuel & Emission
Bulletin No.: 86-65-04
Date: August, 1998
Subject:
Engine High Idle/Flare when Shifting Gears
(Perform Flash Calibration)
Models:
1996-97 Chevrolet and GMC S/T Models
with 4.3L Engine (VINS W, X - RPOs L35, LF6) and Manual Transmission (RPO M5O)
Condition
Some owners may report that the engine exhibits a high idle or flare when shifting gears or disengaging the clutch such as when slowing down or
stopping.
Cause
If following Steps 1, 2 and 3 of the Strategy Based Diagnostics did not reveal a cause, high idle or engine flare may be the result of additional idle air
control (IAC) air that is learned into the stall saver calibration.
Vehicle operation at low road speeds, 16-24 km/h (10-15 mph) in a high gear (5th), causes the engine to lug down below the stall saver threshold. The
off idle stall saver calibration for these engines is approximately 500 RPM.
This situation may be experienced during city driving maneuvers, especially in hilly terrain, when the driver does not downshift the transmission or
depress the clutch and forces the engine RPM under the stall saver threshold.
During this condition, the AC opens to a calibrated level in an attempt to raise the engine RPM above the stall saver threshold. This level of IAC will
cause idle flare if the vehicle is driven out of the lugging condition (ie: downshifting or depressing the clutch) without first coming to an idle. Idling first
would allow the additional idle air to be learned back to a normal level.
Correction