Driveability Symptoms Due to Clogged Fuel Injectors (Clean Injectors)

This bulletin is being revised to update labor time allowance for labor operation J5645. Please discard Corporate Bulletin Number 99-06-04-005A (Section 6 -- Engine).

Some owners may comment on driveability symptoms of long or hard starts, chuggle, rough idle and light or intermittent misfire. The malfunction indicator lamp (MIL) may also illuminate.

Due to various factors, the fuel injectors may become restricted. 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 either trigger the MIL to illuminate or the engine to develop various driveability symptoms.

Fuel injector restrictions, deposits, can be cleaned on the vehicle, using the following procedure. Under NO circumstances should this procedure be modified, changed or shortened.

Notice: 

Important: This bulletin recommends the use of pre-measured containers of GM Top-Engine Cleaner, P/N 12346535, - U.S. USAGE ONLY. Pre-measured containers eliminate the need to measure the amount of GM Top-Engine Cleaner being added to the J 35800-A, injector cleaning tool. In Canada, use P/N 992872. It will be necessary to measure and dispense Top Engine Cleaner into the J 35800-A, injector cleaning tool.

The following tools or their equivalent are required:

1. Disconnect the 10-pin fuel rail electrical connector. Refer to the appropriate Service Information Manual for connector location.
2. Connect the J 39021, fuel injector coil/balance tester, to the J 39021-210, fuel injector selector adapter box.
3. Connect the J 39021-306, fuel injector test harness, to the engine 10-pin fuel rail electrical connector. This allows you to test the fuel injectors without removing the upper intake plenum.
4. Using the injector tester, J 39021, perform an injector balance test. Use the J 39021-210 to select each individual injector. Record the pressure drop of each injector.
5. 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. See the example tables below to determine if cleaning is appropriate.
6. 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.

Maximum Difference: 68-41 = 27 kPa (10-6 = 4 psi)

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. Charge time to labor operation J5650.

Maximum Difference: 48-23 = 25 kPa (7-3 = 4 psi)

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. Charge time to labor operation J5650.

1. Remove the J 39021-306, fuel injector test harness, and reconnect the 10-pin fuel rail electrical connector.

Notice: 

•	GM Top-Engine Cleaner is the only injector cleaning agent recommended. Do not use other cleaning agents, as they may contain methanol which can damage fuel system components.

•	Under NO circumstances should the GM Top-Engine Cleaner 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.

2. For U.S. dealers, empty 2 pre-measured GM Top-Engine Cleaner containers, 24 ml (0.812 oz) each, P/N 12346535, into the J 35800-A, injector cleaning tank. For Canadian Dealers, measure and dispense 48 ml (1.62 oz) of Top-Engine Cleaner, P/N 992872, into the J 35800-A, injector cleaning tank.
3. Fill the injector cleaning tank with regular unleaded gasoline. Be sure to follow all additional instructions provided with the tool.
4. Electrically disable the vehicle fuel pump by removing the fuel pump relay and disconnecting the oil pressure switch connector, if equipped.
5. Connect the J 35800-A to the vehicle fuel rail.

Notice: Do not exceed 170 kPa (25 psi). Exceeding this pressure will allow the cleaning solution to flow past the fuel pressure regulator and into the fuel tank, which may damage the fuel pump and other system components.

6. Pressurize the J 35800-A to 170 kPa (25 psi).
7. Remove the vacuum line from the fuel pressure regulator and plug the vacuum hose.
8. Start and idle the engine until it stalls, due to lack of fuel. This should take approximately 15-20  minutes.
9. Disconnect J 35800-A from the fuel rail.
10. Reconnect the vehicle fuel pump relay and oil pressure switch connector, if equipped.
11. Reconnect the vacuum line to the fuel pressure regulator.
12. Start and idle the vehicle for an additional 2 minutes to ensure residual injector cleaner is flushed from the fuel rail and fuel lines.
13. Repeat Steps 1-5 of the Injector Balance Test, and record the fuel pressure drop from each injector.
14. 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 Information manual for the vehicle.
15. Road test the vehicle to verify that the customer concern has been corrected.

Parts are currently available from GMSPO.

For vehicles serviced under warranty, use:

*An additional 0.7 hour may be claimed on J5645 for performing the injector diagnosis procedure.