LOW SPEED DRIVEABILTY (PROM) NEW KNOCK SENSOR AVAILABLE

Subject: LOW SPEED DRIVEABILITY AND/OR CHECK ENGINE LIGHT CODE 43 (INSTALL KNOCK SENSOR AND MEMCAL OR PROM)

Model and Year: 1990-91 FIREBIRD W/5.0L

This bulletin is being revised to add the 5.0L Port Fuel Injection (VIN F, LB9) V8 engine. This bulletin cancels and supersedes Pontiac Service Bulletin 91-6-2 issued 7/90. Please discard all copies of 91-6-2.

CONDITION: Some owners of 1990 and 1991 F-cars with the 5.OL Port Fuel injection (VIN F, LB9) V8 engine may comment about low speed driveability or a Check Engine Light - Code 43 - Electronic Spark Control (ESC). Comments about LB9 driveability may include idle surge, unstable idle, or stall at stops.

Some owners of 1991 F-cars with the 5.OL Throttle Body Injection (VIN E, L03) V8 engine may also comment about a Check Engine Light - Code 43 (ESC).

CAUSE: New calibrations have been released that refine idle speed control (LB9 only) and ESC diagnostics. A new knock sensor (LB9 Only) is also available which has improved durability characteristics.

CORRECTION: Install knock sensor (LB9 ONLY) P/N 10456126*, and install the applicable Memcal or PROM from the table below:

Service Scanner Broadcast Model Engine Application P/N I/D Code Year ---------- ---- ---- ---- ------ ------------------ **16163062 3061 AXXB 1991 LB9 Automatic with Chevrolet P235/55Rl6

**16163066 3071 AXXC 1991 LB9 Manual (M39) with Chevrolet P235/55Rl6

**16163075 3091 AXXF 1991 LB9 Automatic with P245/50ZR16

**16163070 3081 AXXD 1991 LB9 Manual with P245/50ZRl 6

**16163138 3271 AXYC 1990-91 LB9 Manual (MK6)

**16163137 3261 AXYB 1990 LB9 Manual (M39)

**16163139 3281 AXYD 1990 LB9 Automatic

* 16161107 1091 AXKS 1991 L03 Automatic with California Emissions

* 16161112 1101 AXKT 1991 L03 Automatic with Federal Emissions

* 16161117 1111 AXKU 1991 L03 Manual (M39) with California Emissions

*16161123 1121 AXKW 1991 L03 Manual (M39) with Federal Emissions

* Parts are currently available from GMSPO.

** Parts are expected to be available on March 25, 1991. Until then normal part orders will not be accepted by GMSPO. Only verifiable emergency VIP orders will be accepted. SPO will make every effort to obtain parts. All parts will be placed on 400 control to waive VIP surcharges. However, the part will be shipped premium transportation at dealer's expense. All other order types will be cancelled as incorrectly ordered while the 400 control is in place.

Labor Operation: T0500 (VIN E) Labor Time: 0.4 Hours

Labor Operation: T1710 (Vi N F - Knock Sensor and PROM) Labor Time: .6 Hour

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.