Exhaust System - Boom/Grunt/Groan/Moan/Vibration

Article No.
98-21-1

10/26/98

^ NOISE - "BOOM/GRUNT/GROAN/MOAN" - DURING
IDLE WITH ENGINE HOT OR COLD - 4.0L SOHC
VEHICLES

^ VIBRATION - DURING IDLE WITH ENGINE HOT OR
COLD - 4.0L SOHC VEHICLES

LIGHT TRUCK:
1997-99 EXPLORER, MOUNTAINEER

This TSB article is being republished in its entirety to include additional Figures, additional symptoms and to include 1999 model year vehicles and Mountaineer.

ISSUE
A vehicle vibration may be present during a hot or cold idle condition and/or an audible "boom/grunt/groan/moan" may be present between 700-800 rpm during a cold engine start and low vehicle speed. This concern may be more noticeable on left turns. This may be caused by exhaust system vibration when the engine firing frequency lines up with a resonant frequency of the exhaust system.

ACTION
Install a Y-brace. The brace limits the vertical bending motion of the exhaust system and reduces the possibility of an objectionable vibration. Refer to the following Service Procedure for details.

SERVICE PROCEDURE

1. Reprogram the Powertrain Control Module (PCM) with the latest calibration. Refer to TSB 98-1-18. (Do not reprogram 1998 vehicles built after 2/14/98.) The new calibrations limit the amount of time the vehicle will spend in the critical rpm range.

2. Neutralize the exhaust system as per the 1998 Explorer Workshop Manual, Page 100-04-29.








3. Install a new pressure Power Steering Hose (F87Z-3A719-JA). Isolate the metal lines on the steering assembly (use rubber hose). Refer to Figures 1 and 2

4. Install the new exhaust brace. The top "Y" portion of brace attaches to two (2) bolts at the bottom of the transmission bellhousing per the following process:

a. Install the Y-Brace (F87Z-5K249-AA) and hand start bolts in transmission bellhousing.

b. Attach to the left catalyst converter brace using a 2" U-bolt (F87Z-5A231-BA). Hand start the U-bolt nuts.

c. Torque transmission bellhousing bolts to 30 N.m (22 lb-ft).

d. Torque the U-bolt nuts to 40 N.m (30 lb-ft).





Obtain an Authorized Modifications Decal (FPS 8262 - obtainable through DOES II, 25/pkg) and list the date, dealer number, and summary of modifications performed. Select a prominent place adjacent to the Vehicle Emission Control Information Decal suitable for installing the Authorized Modifications Decal. Clean the area, install the decal, and cover it with a clear plastic decal shield.

PART NUMBER PART NAME

F87Z-5K24S-AA Y-Brace
F87Z-5A231-BA U-Bolt
F87Z-3A71S-JA Power Steering Hose

OTHER APPLICABLE ARTICLES: 98-1-18

SUPERSEDES: 98-15-14

WARRANTY STATUS: Eligible Under The Provisions Of Bumper To Bumper Warranty Coverage

OPERATION DESCRIPTION TIME

982101A Install Service Parts 1.0 Hr.

982101B Reprogram Powertrain 1.5 Hrs.
Control Module (PCM) And
Install Service Parts

DEALER CODING
CONDITION
BASIC PART NO. CODE
RECAL 42

OASIS CODES: 403000 608000, 608400, 702300, 703000, 703100