LOW OR ROUGH IDLE FOLLOW DECEL REVISED HOT IDLE CALIBRATIONS

Subject: LOW OR ROUGH IDLES FOLLOWING DECELERATION

Model and Year: 1990-92 GEO STORM

Condition:

A limited number of Geo Storm R-cars may exhibit low or rough idles immediately following a deceleration.

Cause:

Original ECM (Emission Control Module) calibration did not fully address idle instability at ambient temperatures over 80 degrees F. In severe cases, the low idle may result in a stall. If normal service procedures do not correct the condition, the following calibrations have an improved idle air control feature which will stabilize the rough idles.

NOTE: Some automatic transmission equipped vehicles already have the DOHC engine (VIN Code 5), some late build 1991 base models with SOHC engine (VIN Code 6) and all 1992 base models with the SOHC engine (VIN Code 6). No 1990-92 GEO Storms with manual transmissions were produced with the improved I.A.C. feature.

Emission Engine System Trans 90 MY 91 MY 92 MY --------------- -------- ----- ----------- ----------- ----------- Base 1.6L FED M/T 16174179 16165809 16165809 SOHC VIN 6 A/T 16174189 16165819 16165819

CAL M/T 16174199 16174239 16174239 A/T 16174209 16174249 16174249 ---------------------------------------------------------------------------- GSI DOHC FED M/T 16174129 16174259 16166629 90-91 A/T 16174139 16174269 16166619 1.6L VIN 5 OR 1992 1.8L CAL M/T 16174159 16174279 16166649 VIN 8 A/T 16174169 16174289 16166639

Warranty Information:

Labor Operation: J6355

Use applicable labor time guide for labor hours.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.