Exhaust - Catalytic Converter Odor/Rough Idle
GMC NUMBER: 88-T-213GROUP: 6E - Engine Emission
DATE: September, 1989
CORPORATE NUMBER: 936517
SUBJECT:
ROUGH IDLE AND/OR CONVERTER ODOR
(SERVICE PROCEDURE - 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 he addressed by relocating the oxygen sensor from the left hand exhaust manifold to the exhaust takedown (Y-pipe) and installing the appropriate calibration PROM.
To accomplish this, it will he necessary to obtain the parts listed below:
Qty Description Part Number
1 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 install 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 (PIN 10017198) in the former oxygen sensor location in the left side exhaust manifold.
8) Install the appropriate calibration PROM from the Application 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