Hombre S Regular Cab 4WD V6-4.3L (1999)
Technical Service Bulletin # SB03-02-S003
Date: 030401
Fuel System - SES Lamp ON/Rough Idle
TSB SB03-02-S003
Rough Idle After Start andlor a SES Light (Unstick and Clean
CSFI Poppet Valves or Convert to MFI)
Rough Idle After Start and/or a Service Engine Soon
(SES) Light (Unstick and Clean Central Sequential Fuel
Injection (CSFI) Poppet Valves or Convert to MFI)
ISSUE DATE: APRIL 2003
Affected Vehicles
1997-2000 Isuzu Hombre (TH) models equipped with a 4.3L engine.
Service Information
Condition:
Some customers may comment on rough idle after start-up, especially if the vehicle has sat overnight. These symptoms may be intermittent. The Service
Engine Soon (SES) light may also be illuminated. Current misfire or history misfire codes may be detected with the Tech 2 scan tool.
Cause:
A deposit build-up on the CSFI poppet valve ball and/or seat may cause the poppet ball to stick open or closed. In either case, the specific cylinder will
be mis-fueled, resulting in a cylinder mis-fire condition.
Correction:
A new injector unsticking and cleaning process has proven to be effective in restoring poppet valves to an as new condition. CSFI injector replacement
should NOT be considered as a correction for this customer concern.
Check the vehicle history to determine if the vehicle is returning for a second fuel system repair for this condition. If the fuel system has been repaired
for this condition previously, then inform the customer that an alternate fix is available. A new Multiport Flexible Injection (MFI) fuel system has been
developed that will back service the CSFI fuel system. The MFI fuel system eliminates the CSFI poppet valve ball and seat. The CSFI fuel system will
need to be replaced as a unit. Refer to CSFI to MFI Conversion instructions in this bulletin.
NOTICE:
Individual CSFI injectors cannot be replaced with MFI injectors. The entire CSFI fuel meter body will need to be replaced. The bracket used to retain
the injectors in the fuel meter body is different between the CSFI and MFI uniL The unit may not seal if you mix injectors. NOTE: If injectors are mixed
severe engine damage could resulL
Cleaning the CSFI injectors is the preferred repair. The CSFI unit should not be replaced until cleaning has been attempted. If the vehicle should return
for the same repair, then the CSFI unit can be replaced with an MFI unit. If the vehicle is out of warranty, the customer should be given the option of
which fix to pursue.
The first step of this process is to use the J1413 Evap Pressure/Purge Station, in conjunction with the J44466-10 pressure regulator/hose assembly, to
provide the required high pressure (150 psi) source to perform the unsticking procedure. The J39021 fuel injector tester and accessories provide the
means to "energize" the injector. Some later model-year vehicles may utilize the Tech 2 to "energize" the injectors.
The second step of this process is to run the engine on a solution of 10% Top Engine Cleaner and 90% gasoline. This will effectively clean any deposits
from the ball and seats of the poppets. It is very important that the engine fuel system is separated from the vehicle fuel system. Top Engine Cleaner may
have detrimental effects on the fuel pump.
