PROM - Hesitation On Heavy Acceleration/Engine Miss In N
BULLETIN NO.: 94-T-01ISSUE DATE: January, 1994
GROUP/SEQ. NO.: Engine-01
CORPORATION NO.: 386001
SUBJECT:
Hesitation On Heavy Acceleration-Automatic Transaxle, Engine Miss in Neutral-Manual Transaxle, SOHC (LKO) Engine (Install New PCM Calibration)
MODELS AFFECTED:
1994 Saturns built before and including vehicle identification number VIN RZ224246 for vehicles equipped with automatic transaxles and VIN RZ224395 for vehicles equipped with manual transaxles.
IMPORTANT:
1994 Saturns built after the above VIN breakpoints have the new PCM calibration installed.
CONDITION:
On SOHC (LKO) engines with automatic transaxles, some owners may comment that the engine hesitates under heavy acceleration during engine warm-up (coolant temperature below 70~C [158~F]). On SOHC (LKO) engines with manual transaxies, some owners may comment that the engine misses between 1500-2000 rpm in Neutral with engine at normal operating temperature.
CAUSE:
Due to engine sensitivity to variations in cool ambient temperatures, along with Federal regulations that address spring and summer fuel grade volatility, initial start-up and warm-up driveability can be impacted.
CORRECTION:
For vehicles equipped with automatic transaxles, verify that the vehicle hesitates during heavy acceleration with the engine coolant temperature below 70~C (158~F). For vehicles equipped with manual transaxles, verify that the engine misses between 1500-2000 rpm in Neutral with the engine at normal operating temperature.
If a concern is verified, proceed to the procedure in this bulletin.
PROCEDURE:
1. Use the Scan tool to check for PCM EC and TC diagnostic trouble codes and flags. If diagnostic trouble codes or flags are present, refer to the appropriate chart in the "Electronic Engine Controls" or "Automatic Transaxle" service manual and repair the condition. After verifying that the condition has been repaired, refer to step 4.
2. If no diagnostic trouble codes or flags are present, monitor Scan tool data and verify all parameters are within specification. Refer to the "Scan Tool General Information Table" in the "Electronic Engine Controls" service manual. If parameters are not within specification, repair the condition. After verifying that the condition has been repaired, refer to step 4.
3. If no diagnostic trouble codes or flags are present and Scan tool data is within specifications, refer to step 4.
4. Download the new calibration using the Saturn Service Stall System. (Refer to the "Service Stall System User Guide" or "Electronic Engine Controls Service Manual" for download instructions.)
IMPORTANT:
Before installing the new engine calibration, make a note of the transaxle calibration installed, and download the same transaxle calibration with the current engine calibration.
CLAIM INFORMATION:
To receive credit for this repair, submit a claim through the Saturn Dealer System as follows: (see illustration)