Engine - Rough Idle and/or Converter Odor
89chevy20Number: 88-424-6E
Section: 6E
Date: July, 1989
Subject: ROUGH IDLE AND/OR CONVERTER ODOR
Model and Year: 1988 C1, C2, K1, K2 TRUCKS WITH 4.3L (VIN CODE Z) ENGINE
TO: ALL CHEVROLET DEALERS
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 relocation 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:
Quantity Description Part Number
1 Exhaust Y-pipe 15620225
1 Plug 10017198
2 Seal 15522434
1 Calibration PROM See Application Table
Parts are currently available from 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. Install it in the boss provided in the newly installed Y-pipe using a small amount of ant-seize compound as described in the Service Manual. Torque the sensor to 30 ft-lb.
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 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 Hrs
APPLICATION TABLE
NOTES:
TRUCK MODEL DESCRIPTION EMISSIONS PACKAGE DESCRIPTION
C = All C-trucks NA5 = Federal Emissions
C1 = All C10-trucks NA6 - High Attitude Emissions
C2 = All C20-trucks NB2 = California Emissions
K = All
K-trucks
K1 = All
K10-trucks
K2 = All
K20-truckS
K100 53 = K10 w/Extended Cab