Engine - High Idle/Flare when Shifting Gears
File In Section: 6E - Engine Fuel & EmissionBulletin 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
Perform flash calibration. Refer to the table for the applicable calibration change. Perform the programming per the latest Tech line information for programming procedures.
The new calibrations reduce the number of stall saver counts that can be learned while lugging the engine. In addition, these new calibrations minimize turning on the MIL lamp due to temporary overheating of the oxygen sensors.
Important:
The calibrations listed are FLASH calibrations and are not available from GMSPO. These calibrations are available on 1998 Techline CD ROM Disc 07 and later.
Warranty Information
For vehicles repaired under warranty, use the table.
Labor Operation Description Labor Time
J6355 Reprogramming Use Published Labor
Operation Time