ROUGH IDLE AND/OR CONVERTER ODOR (SERVICE PROCED.-NEW PROM
MODELS: 1988 C1, C2, K1, K2 TRUCKS WITH 4.3L ENGINE (VIN CODE Z)
Some 1988 C/K trucks equipped with 4.3L (VIN Code Z) engines may exhibit an exhaust odor often described as sulfur or rotten egg smell at idle following sustained highway driving or trailer towing. Additionally, some trucks may exhibit rough or unstable idle quality.
These conditions may generally be addressed by relocating the oxygen sensor from the left hand exhaust manifold to the exhaust takedown (Y-pipe) and installing the appropriate calibration PROM.
PARTS REQUIRED:
To accomplish this, it will be necessary to obtain the parts listed below:
Qty. Description Part Number ---- ----------- ----------- i Exhaust Y-pipe 15620225 1 Plug 10017198 2 Seal 15522434 1 Calibration PROM See Application Table
Parts are currently available form GMSPO.
SERVICE PROCEDURE:
1) Disconnect the battery.
2) Remove the exhaust Y-pipe and discard.
3) Install new Y-pipe (P/N 15620225). It may be necessary to replace the exhaust manifold to Y-pipe seals (P/N 15522434) prior to installing the new Y-pipe.
4) Remove the oxygen sensor from the left side exhaust manifold and instal it in the boss provided in the newly installed Y-pipe using a small amount of anti-seize compound as described in the Service Manual. Torque the sensor to 30 ft-lb (41 N-M).
5) Remove the wiring harness cover located at the rear of the engine, see Illustration.
6) Untape the existing oxygen sensor lead wire a short distance up the harness and reroute as shown in the Illustration. No splicing is necessary.
IMPORTANT: Assure that the lead wire does not contact the sharp edge of the dipstick tube bracket.
7) Install plug (P/N 10017198) in the former oxygen sensor location in the left side exhaust manifold.
8) Install the appropriate calibration PROM from the Apphcation Table.
9) Reconnect the battery.
10) Run the engine and check the exhaust manifold to Y-pipe connections for leaks. Repair any leaks found. If a leak exists between the engine and the oxygen sensor location, it may cause the exhaust odor and/or unstable idle quality conditions to continue.
Labor Operation Number: T7965 Labor Time: 1.4 Hours
APPLICATION TABLE
NEW NEW B/CAST PROM BODY EMISS. CODE I.D. STYLE TYPE NEW PROM (PROM SCAN ----- ---- TRANS AXLE KIT LABEL) TOOL ----- ---- --- ------ ---- 4.3L ENGINE (RPO B4) C1, C2 NA5/NA6 M40 K1, K2 FED/ALT 3 SPD AUTO ALL 16121150 AKRZ 3441 C1, C2 NA5/NA6 MD8 K1, K2 FED/ALT 4 SPD AUTO ALL 16121154 AKSB 3461 C2 NA5/NA6 M20 K1, K2 FED/ALT 4 SPD MAN ALL 16121166 AKSK 3521 NA5/NA6 M20 FED/ALT 4 SPD MAN ALL 16121162 AKSJ 3511 C1, C2 NA5/NA6 MG5 K1, K2 FED/ALT 5 SPD MAN ALL 16121158 AKSF 3491 C1, C2 NB2 MD8 K1, K2 CAL 4 SPD AUTO ALL 16121198 AKSM 3541 C1, C2 NB2 M20 K1, K2 CAL 4 SPD MAN ALL 16121170 AKSL 3531 C1, C2 NB2 MG5 K1, K2 CAL 5 SPD MAN ALL 16121174 AKSN 3551
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.
