2007 Chevy Truck Injection system

  • V8
  • 2WD
  • 41,272 MILES
The vehicle is misfiring on #7 & 8 cylinders. Replaced plugs and wires. Exchanged coils and injectors - same problem on same cylinders. Can unplug #1 and #7 will clear up and fire and #1 & 8 will be misfiring. What can this be? Thank you.
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have the same problem?
Monday, August 25th, 2008 AT 1:46 PM

1 Reply

This is what i have on this
hope it help

Can u elaborate on disconnecting #1 and #7 issue

Various Driveability Symptoms Due to Clogged Fuel Injectors, MIL/SES DTCs P0171, P ...
Various Driveability Symptoms Due to Clogged Fuel Injectors, MIL/SES DTCs (Clean Fuel Injectors and/or Perform Injector Test With AFIT - CH-47976)
Reference Number(s): 03-06-04-030F, Date of Issue: December 10, 2007 2000-2008 GM Passenger Cars and Light Duty Trucks (Including Saturn); 2003-2008 HUMMER H2; 2006-2008 HUMMER H3; 2005-2008 Saab 9-7X; with 2.0L, 2.2L, 2.4L, 2.8L, 3.1L, 3.4L, 3.5L, 3.8L, 3.9L, 4.2L, 4.3L, 4.8L, 5.3L, 6.0L, 6.2L or 8.1L Engine (VINs X, F, D, 4, 5, T, 8, J, E, H, L, 6, K, 1, 2, R, W, S, X, V, T, M, N, U, H, Y, 8, G - RPOs LNF, L61, LN2, L43, LD9, LK5, LG8, LA1, LX5, LX9, LZ4, LZE, L52, L36, L67, L26, LZ9, LZ8, LGD, LL8, LU3, LR4, LM7, LH6, LQ9, LQ4, LS2, L76, L92, L18); and MULTEC 2 Fuel Injectors Supercedes: This bulletin is being revised to update the model year to 2008. Please discard Corporate Bulletin Number 03-06-04-030E (Section 06 - Engine/Propulsion System). Affected Model(s):
Related Ref Number(s): 03-06-04-030, 03-06-04-030A, 03-06-04-030B, 03-06-04-030C, 03-06-04-030D, 03-06-04-030E, 03-06-04-030F

Some customers may comment on any of the following various driveability symptoms:
Extended Crank Time
Hard to Start
MIL/SES Illuminated with DTCs
Lack of Power
Surge or Chuggle
Rough Idle
Light or Intermittent Misfire
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.
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. As a long term solution, and to prevent reoccurrence, customers should be encouraged to use Top Tier Detergent Gasoline .

NOTE: GM UPPER ENGINE AND FUEL INJECTOR 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 Upper Engine and Fuel Injector Cleaner, and can assure its compatibility with General Motors fuel system components, as long as the cleaning procedure is followed correctly.
The following tools, or their equivalent, are required:
? CH-47976 Active Fuel Injector Tester (AFIT)
? 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
? * One bottle of GM Upper Engine and Fuel Injector Cleaner, P/N 88861802 (in Canada, P/N 88861804)
? * One bottle of GM Fuel System Treatment Plus, P/N 88861011 (in Canada, P/N 88861012)
Some dealers may not have an Active Fuel Injector Tester (AFIT- CH-47976). Dealers can contact 1-800-GM-TOOLS (1-800-468-6657) to order an AFIT- CH-47976. Dealers still can test the fuel injectors without an AFIT. Refer to Fuel Injector Diagnosis (w/ J 39021 or Tech 2 ) in SI.
IMPORTANT: As mentioned in the AFIT User Guide, vehicles that are not listed in the AFIT menu can still be tested with the AFIT. Depending on the model, it may be possible to enter the previous model year and proceed with testing using the DLC connection. If this is not possible on the model that you are working on, it will be necessary to use the direct connection method outlined in the AFIT User Guide (See Pages 17-31).
General Motors recommends that the Active Fuel Injector Tester (AFIT) be used in testing fuel injectors. If the SI diagnostics do not isolate a cause for this concern, use the Active Fuel Injector Tester (AFIT - CH-47976) to perform an "Injector Test" as outlined in the AFIT User Guide.
The AFIT "Injector Test" measures the flow characteristics of all fuel injectors, which is more precise when compared with the standard Tech 2 fuel injector balance test. As a result, the AFIT is more

likely to isolate the cause of a P1174 DTC (for example: if it is being caused by a fuel injector concern).
The CH-47976 (Active Fuel Injector Tester - AFIT) can also be used to measure fuel pressure and fuel system leak down. Also, as mentioned in the P1174 SI diagnosis, if the misfire current counters or misfire graph indicate any misfires, it may be an indicator of the cylinder that is causing the concern. Refer to Fuel Injector Diagnosis (w/CH-47976) in SI for additional instructions.
To access the training video on AFIT, take the following path at the GM Training Website:
1.After logging into the gmtraining.com website, choose the link on the left side of the page titled "web video library." 2.Then choose "technical." 3.Next, within the search box, type in September course number "10206.09D. 4.This will bring up a link with this course. Scroll through to choose "feature topic." 5.At this point, the seminar can be chosen to view or the video related to the AFIT.
Additional training is available from the gmtraining.com website. Please see TECHassist 16044.18T2 Active Fuel Injector Tester and also see 16044.14D1 GM Powertrain Performance for more information on GM Upper Engine and Fuel Injector Cleaner.
Also, dealers can now download software updates for the AFIT at GM Dealer Equipment (GMDE) on the web at
To access the training video on AFIT, take the following path at the GMPro LMS Training Website:

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