2001 Impala

[way2old]

Hey guys. Are there any TSB's that address a stutter at idle when first starting? It has the 2nd gen 3800. Just wondering. Local dealers are supposed to be friends, but they want to fix and charge. Thanks.

[DanD]

There are a couple of them Tom and they all have to do with cleaning the Injectors and or replacing any after doing an injector balance test.

This bulletin is being revised to update the procedure, models and model years. Please discard Corporate Bulletin Number 03-06-04-030 (Section 06 -- Engine).
Condition
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.
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 either trigger the MIL to illuminate or the engine to develop various driveability symptoms.
Correction
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: The recommended mixture amount of GM Top-Engine Cleaner 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 is the only injector cleaning agent approved for use with General Motors fuel system components. Other injector cleaners may cause damage to plastics, plated metals or bearings. General Motors has completed extensive laboratory testing of GM Top-Engine Cleaner, and can assure its compatibility with General Motors fuel system components, as long as the cleaning procedure is followed correctly.
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.

[DanD]

Here are a couple of examples of injector flow test results.
There is also something about the terminals as well.
And here I thought fretting was what my wife does when I go out with the boys. LOL

Dan.

Injector Balance Test
The following tools, or their 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 12346535, U.S. USAGE ONLY. In Canada, use P/N 992872, 443.6 ml (15 oz) bottle. It will be necessary to measure and dispense 48 ml (1.6 oz) of Top Engine-Cleaner into the J 35800-A, injector cleaning tool twice during this procedure. See Injector Cleaning Procedure below for further information.
Important: Analysis of returned Multec II injectors indicate that terminal fretting corrosion may also be responsible for the conditions described in this bulletin. Since fretting corrosion (microscopic in nature) is nearly impossible to detect in the field, the following steps should be taken to ensure that fretting corrosion is not an issue before performing any additional diagnostics.
Fretting is a term used to describe a tiny rubbing motion that occurs between two surfaces. Fretting corrosion refers to a build up of insulating, oxidized debris that forms on electrical connections due to a fretting action at the contact points. Injector vibration, engine vibration, and electrical harness movement are contributors to the fretting motion.
Depending on how large the build-up of oxide is will determine how drastic the effect will be on the injector circuit. Worst case is a total loss of continuity in the connection resulting in P0200 (Injector Circuit Fault) and P0300 (Misfire) codes being set. If the oxides create a high resistance circuit, insufficient current will be available to properly open the injector, resulting in unstable fuel delivery and ultimately a P0300 DTC. High resistance in the circuit will not necessarily set a DTC P0200. Keep in mind that a connection with fretting corrosion is unstable. Since movement causes fretting, any vibration may create a condition where the connection varies from an open circuit, to a high resistance connection, to a good connection.
Important: Unless intermittent mis-fire due to fretting corrosion is suspected when servicing 3.1L and 3.4L engines, skip steps 1 through 4. Steps 1 through 4 may be performed at a future date when the upper intake is removed.
When servicing 2.8L, 3.5L or 4.2L engines (VINs 8, 6, S -- RPOs LK5, L52, LL8) skip steps 1 through 4 unless replacing injectors.
1. Disconnect one injector electrical connector.
2. Apply a small amount, about the size of a BB, of dielectric grease, P/N 12377900 (in Canada, P/N 10953529) to the female terminal. Be sure to cover both cavities.
3. Reconnect electrical connector to injector.
4. Repeat steps 1 through 3 for all remaining injectors.
5. Using the Tech 2®, perform an injector balance test using the procedure in the appropriate Service Manual. Use the Tech 2® to select each individual injector. Record the pressure drop of each injector on the repair order.
Important: Technicians must record the results of all injector balance tests and keep them with the repair order. For your convenience, the bulletin has a worksheet at the end for recording the test results.
6. Subtract the lowest pressure drop, leanest injector, from the highest pressure drop, richest injector. If there is greater than or equal to a 20 kPa 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.
7. If there is less than a 20 kPa difference, between the highest and lowest fuel pressure drop, the fuel injectors are operating properly and further Service Manual diagnostics should be performed on the vehicle. All diagnostic time should be added to the appropriate labor operation for the repair performed and not to injector cleaning.

Example One

Injector Number Pressure Drop
1 43 kPa)
2 68 kPa
3 42 kPa
4 41 kPa
5 44 kPa
6 42 kPa (6 psi)
Maximum Difference: 68-41 = 27 kPa
Although the pressure drop is greater than or equal to 20 kPa, 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.
Important: When replacing injectors be sure to add dielectric grease to injector electrical connectors.

Example Two

Injector Number Pressure Drop
1 23 kPa
2 48 kPa
3 24 kPa
4 43 kPa
5 44 kPa
6 46 kPa
Maximum Difference: 48-23 = 25 kPa
The pressure drop is greater than or equal to 20 kPa. 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.

[Venturi]

Hey Tom what’s the condition of the secondary ignition system on this thing? I’ve run a crossed quite a few of these with carbon tracked insulators on the plugs.

[way2old]

I think it was the injectors. We cleaned the injectors and held it for a cold start and it seemed fine. The officer did not say how often it did it though. If he returns, I will have the ignition system checked. Thanks guys.