Ignition System - Runs Rough/Misfire DTC's When Wet
2007 Service BulletinsTSB SB07-11-S001
ISSUE DATE: JANUARY 2007
4.2L LL8 Engine - Flashing and/or MIL Light, Rough Idle, Misfire(s) DTC(s) P0300, P0301, P0302, P0303, P0304, P0305, P0306 (This Bulletin Supersedes SB06-11-S016)
Affected Vehicles
2003-2007 Isuzu Ascender (US/UT) with 4.2L Engine
Service Information
This bulletin is being revised to add additional parts information.
Condition:
Some customers may comment that, after severe weather that includes large amounts of rain in a short period of time, the engine has a rough idle and/or flashing MIL light. Upon further investigation, there may be the following DTC(s): P0300, P0301, P0302, P0303, P0304, P0305 or P0306.
This condition can be aggravated if the vehicle is parked nose down on an incline during this type of weather. The customer may also comment on repeat occurrences of this condition because water may be passing over
the Air Intake Plenum (AIP).
Possible Cause:
The dripping rain water onto the engine cam cover will collect at the coil(s) and may seep past the coil(s) into the spark plug(s) well of the cylinder head and may affect the operation of the spark plug(s) and coil(s), causing the misfire(s).
Correction:
Install Air Inlet Grille Panel (AIP) seal.
Service Procedure
IMPORTANT:
Before replacing the AIP seal, refer to Misfire diagnostics in the Service Manual to determine if water intrusion is the cause of the misfire.
Diagnostic Aids for Misfire
^ Refer to the Service Manual for Base Engine Misfire without Internal Engine Noises.
^ If no trouble found (NTF) using the Service Manual diagnosis on Base Engine Misfire without Internal Engine Noises, then refer to the Service Manual for Misfire DTC(s).
^ If Misfire diagnostic leads to the removal of the coil(s) and spark plug(s), refer to the Service Manual diagnosis.
a) Air Cleaner Outlet Resonator Replacement.
b) Ignition Coil Replacement Removal Procedure.
c) Spark Plug Replacement.
^ Coil(s) damage from water intrusion will have a film of white chalk build-up on the outside and inside of the spark plug boot to ignition coil(s) assembly. If present, remove the spark plug(s) and inspect for similar build-up on the outside of the spark plug(s).
^ If NTF with the coil(s) and spark plug(s), continue on with the Misfire Diagnostic in the Service Manual.
^ Replace any coil and spark plug that has been diagnosed to be damaged from water intrusion.
To prevent a reoccurrence, follow repair information outlined in this bulletin to replace the AIP seal.
IMPORTANT:
To prevent a repeat occurrence of the above condition, Do Not return the vehicle to the customer without replacing the AIP seal if water intrusion was determined to be the cause.
If water intrusion was determined to be the cause for the replacement of the spark plug(s) and/or coil(s), the AIP seal should be replaced.
^ Installation of AIP Seal
To prevent a reoccurrence, the AIP seal will redirect the rain water flow away from the engine cam cover area.
The following repair information outlined in this bulletin will assist technicians in the replacement of the revised AIP seal.
1. Remove the original rear hood (AIP) seal (1) to the air inlet grille panel staked studs.
2. Cut three or four slits through the original rear hood (AIP) seal to the air inlet grille panel plastic staked studs (1). Carefully remove the rear hood (AIP) seal from the staked plastic studs.
Do Not cut off the top or staked portion of the plastic studs holding the rear hood (AIP) seal to the air inlet grille panel. If removed, the air inlet grille panel will have to be replaced.
3. Remove any dirt or debris from the sealing surface of the air inlet grille panel.
4. Install AIP seal, P/N 8-25788-476-0. The seal (1) has a foam weatherstrip attached to the bottom. The foam weatherstrip faces the air inlet grille panel. Carefully stretch the AIP rubber seal over the plastic staked studs of the air inlet grille panel without damaging them.
Parts Information
Warranty Claim Information
Use the labor operation shown.