Fuel System - Multiple Driveability Symptoms
TSB SBO4-02-S002Multiple Driveability Symptoms Due To Clogged Fuel Injectors
(Clean Injectors)
ISSUE DATE: FEBRUARY 2004
Affected Vehicles
2003-2004 Ascender (US) models equipped with 4.2L L6 engines.
Service Information
Condition:
Some owners may comment on driveability symptoms on long or hard starts, rough idle and light or intermittent misfire. The malfunction indicator lamp (MIL) may also light up.
Possible Cause:
Due to various factors, the fuel injectors may become restricted. Extensive testing has demonstrated that fuel related issues are the cause of clogged injectors. At this point, no specific fuel, fuel constituent, or engine condition has been identified as causing the restriction. The restriction causes the engine to operate at a lean air fuel ratio. This may trigger either the MIL to light up or the engine to develop various driveability symptoms.
Correction:
Fuel injector restrictions and/or deposits, can be cleaned using the following procedure:
^ Under NO circumstances should this procedure be modified, changed or shortened.
^ The recommended mixture amount of GM Top-Engine Cleaner P/N 8-12346-535-0 has been increased from 5% used in prior procedures to 10%. This increase was implemented to improve the effectiveness of the injector cleaning procedure. Follow the cleaning procedure carefully to minimize the risk of fuel system damage. Testing has demonstrated that exceeding the 10% cleaning solution concentration does not improve the effectiveness of this procedure. GM Top - Engine Cleaner P/N 8-12346-535-0 is the only injector-cleaning agent approved for use with GM manufactured fuel system components. Other injector cleaners, while effective, may cause damage to plastics, plated metals or bearings. The Manufacturer, GM has completed extensive laboratory testing of the GM Top - Engine Cleaner PIN 8-12346-535-0, and can assure its compatibility with GM fuel system components, as long as the cleaning procedure is followed correctly.
^ This bulletin recommends the use of pre-measured containers of GM Top-Engine Cleaner P/N 8-12346-535-0, U.S. USAGE ONLY. Pre-measured containers eliminate the need to measure the precise amount of GM Top-Engine Cleaner P/N 8-12346-535-0 being added to the J 35800-A, injector cleaning tool.
Service Procedure
Injector service may consist of the following procedures:
^ Injector Balance Test
^ Injector Cleaning
^ Injector Replacement
Injector Balance Test
The following tools or equivalent, are required:
^ J 35800-A Fuel Injector Cleaner
^ J 37287 Fuel Line Shut-off Adapter
^ J 42964 Fuel Line Shut-off Adapter
^ J 42873 Fuel Line Shut-off Adapter
^ Four pre-measured GM Top-Engine Cleaner Containers, 24 ml (0.812 oz) each, P/N 8-12346-535-0.
1. Use the Tech 2 to select each individual injector with the Tech 2 balance test function. Record the pressure drop of each injector on the repair order.
NOTE:
It is mandatory that the dealer record the results of the Injector Balance Test on the repair order.
2. Subtract the lowest pressure drop, leanest injector, from the highest-pressure drop, richest injector. If there is more than a 20 kPa (3 psi) difference between the lowest and highest-pressure drop, then the fuel injectors may be the cause of the driveability symptom.
3. If there is a 20 kPa (3 psi) difference, or less, between the highest and lowest fuel pressure drop, the fuel injectors are operating properly and further diagnostics should be performed on the vehicle (see example 1).
Although the pressure drop is greater than 20 kPa (3 psi), cylinder 2 stands out as being rich when compared to the other injectors, do not clean the injectors. Replace injector number 2, (Example 1, the Technician is replacing injector no. 2).
In Example 2, the pressure drop is greater than 20 kPa (3 psi). Injectors 1 and 3 appear to be lean when compared to injectors 2, 4, 5 and 6. Clean and re-test pressure drop. If cleaning does not restore flow on injectors 1 or 3, replace the defective injector or injectors as necessary.
Injector Cleaning Procedures
NOTE:
^ GM Top-Engine Cleaner P/N 8-12346-535-0 is the only injector-cleaning agent recommended. DO NOT USE OTHER CLEANING AGENTS, AS THEY MAY CONTAIN METHANOL THAT CAN DAMAGE FUEL SYSTEM COMPONENTS. Under NO circumstances should the GM Top-Engine Cleaner P/N 8-12346-535-0 be added to the vehicle fuel tank, as it may damage the fuel pump and other system components.
^ Do not exceed a 10% cleaning solution concentration. Higher concentrations may damage fuel system components. Testing has demonstrated that exceeding the 10% cleaning solution concentration does not improve the effectiveness of this procedure.
^ During this procedure, you will need a total of 960 ml (32.4 oz) of cleaning solution (10% GM Top-Engine Cleaner P/N 8-12346-535-0/90% Regular Unleaded Gasoline). That is two tanks of solution for the J 35800-A Fuel Injector Cleaner Tank. Other brands of tools may have a different capacity and would therefore require more or less tanks to complete the procedure. You must use all 960 ml (32.4 oz) of solution (10% GM Top-Engine Cleaner P/N 8-12346-535-0/90% Regular Unleaded Gasoline) to insure complete injector cleaning.
1. Empty 2 pre-measured GM Top-Engine Cleaner containers, 24 ml (0.812 oz) each, P/N 8-12346-535-0, into the J 35800-A, injector cleaning tank. If you are using any other brand of tank, you will need a total of 96 ml (3.24 oz) of GM Top-Engine Cleaner P/N 8-12346-535-0 mixed with 864 ml (29.16 oz) of regular unleaded gasoline.
2. Fill the injector-cleaning tank with regular unleaded gasoline. Be sure to follow all additional instructions provided with the tool.
3. Electrically disable the vehicle fuel pump by removing the fuel pump relay and disconnecting the oil pressure switch connector, if equipped.
4. Relieve fuel pressure and disconnect the fuel feed and return lines at the fuel rail. Plug the fuel feed and return lines coming off the fuel rail with J 37287, J 42874 or J 42964 as appropriate for the fuel system.
5. Connect the J 35800-A to the vehicle fuel rail.
6. Pressurize the J 35800-A to 510 kPa (75 psi).
7. Start and idle the engine until it stalls, due to lack of fuel. This should take approximately 15-20 minutes.
8. Refill the J 35800-A injector-cleaning tank per steps 1 and 2.
9. Restart and idle the engine until it stalls, due to lack of fuel. This should take approximately 15-20 minutes.
10. Disconnect J 35800-A from the fuel rail.
11. Reconnect the vehicle fuel pump relay and oil pressure switch connector, if equipped.
12. Remove the J 37287, J 42874 or J 42964 and reconnect the vehicle fuel feed and return lines.
13. Start and idle the vehicle for an additional 2 minutes to ensure residual injector cleaner is flushed from the fuel rail and fuel lines.
14. Use the Tech 2 to select each individual injector with the Tech 2 balance test function. Record the pressure drop of each injector on the repair order.
15. Subtract the lowest fuel pressure drop from the highest fuel pressure drop. If the value is 15 kPa (2 psi) or less, no additional action is required. If the value is greater than 15 kPa (2 psi), replace the injector assembly with the lowest fuel pressure drop (follow injector replacement procedures outlined in the appropriate Service Manual).
16. Add one ounce (30 ml) of Fuel System Treatment, P/N 8-12345-104-0 to the vehicle fuel tank for each gallon (3.78 L) of gasoline estimated to be in the fuel tank. Instruct the customer to add the remainder of the bottle of Fuel System Treatment to the vehicle fuel tank at the next fill-up.
17. Advise customer to change brands of fuel and to add Isuzu Fuel System Treatment every 3000 miles (4800 km). Regular use of Isuzu Fuel System Treatment should keep the customer from having to repeat the injector cleaning procedure.
18. Road test the vehicle to verify that the customer concern has been corrected.
Parts Information
Warranty Claim Information
Use the labor operations shown.
Disclaimer