2008 6.0l Vvt - Rough Idle/missing

corneredge · November 8, 2007

My brand new 6.0L suburban engine is running terribly. At idle it misses bad enough that you can feel it shaking the truck. At part throttle on the road I can feel it miss. Often when I lean into the throttle for a downshift, it misses before/during the shift and the trans shifts harder/bad.

Recently I also get a vibration over 50mph whenever the engine goes into V4 mode.

My dealer on first visit about it right after I picked up the truck insists "there is no problem" because there are no error codes in the computer. I'm going to go back to him again tomorrow.

I've had the truck for 2-3 weeks, I have 1000 miles on it. What do you recommend I ask for next? A compression test? I feel like I have a bad engine with a cylinder that's not up to snuff.

Thanks for the advice, a new engine with VVT should not idle or run this bad.

-Russ

Import Hater · November 8, 2007

Could be a longshot, but is an engine mount broken?

corneredge · November 8, 2007

Thanks, I'll check.

jpshea88 · January 7, 2008

Hey guys, sorry to bring back an old topic, but I have the same issue.

Since new in May 2007. My avalanche 6.0 VVT is rough idling and poor low end. Poor shifts, power steering isn't smooth and sometimes cuts out. The engine cuts out at stop lights. Can feel the truck let off the brakes and then push again. At time dealer said the engine needed to break-in. And I bought it. So at 2400miles I brought it back for an oil change plus check rough idle.

Well, they changed the oil and gave the truck back. Didn't even look because there is no code.

Went to two seperate dealers, no service because no engine light.

One dealer was willing to admit the idle was unusually rough, but on paper. And said without codes they can't diagnose.

To me, I can understand a flat rate tech not wanting to take this on.

Is there any way I can convince the dealer to give it a shot. Maybe on a slow day.

I am sure it's a vacuum leak. At idle vacuum is just under 16 inches.

Kanima · January 10, 2008

I have the same Issue on my 6.0 I put it in the shop today here is the tsb on the problem but I not sure it will fix the missiing I feel at 55 60.

*Subject:**LY6 Cold Start Idle Concern, Engine Sags While Shifting Into Drive or Reverse (Reprogram PCM) #07-06-04-007 - (03/05/2007)*

*Models:**2007 Chevrolet Silverado HD*

*2007 GMC Sierra HD*

*with Vortec™ 6.0L V8 Engine (VIN K -- RPO LY6)*

*Condition*

<http://service.gm.com/servlets/BlobShtml?ShtmlFile=1912687&pubid=1647&evc=sm#ss1-1912687>Some customers may comment that the vehicle's engine sags while shifting into drive or reverse when it is cold outside.

*Cause*

<http://service.gm.com/servlets/BlobShtml?ShtmlFile=1912687&pubid=1647&evc=sm#ss2-1912687>The powertrain control module (PCM) calibration may allow the vehicle's engine idle to sag when the engine coolant temperatures are around 8°C (47°F) while shifting into drive or reverse.

*Correction*

<http://service.gm.com/servlets/BlobShtml?ShtmlFile=1912687&pubid=1647&evc=sm#ss3-1912687>Reprogram the PCM with the updated calibration.

Due to the length of this programming event, we strongly recommend the following precautions:

*Notice: *Before reprogramming, check the battery condition to prevent a reprogramming error of any of the modules due to battery discharge. Battery voltage must be between 12 and 16 volts during reprogramming. If the vehicle battery is not fully charged, use jumper cables from an additional battery. Be sure to turn off or disable any system that may put a load on the battery, such as automatic headlamps, daytime running lights, interior lights, heating, ventilation, and air conditioning (HVAC) system, radio, engine cooling fan, etc. A programming failure or control module damage may occur if battery voltage guidelines are not observed.

To maintain battery voltage during programming, make sure you are using an approved battery charger such as the Midtronics Charger, PSC 300 or PSC550. You may also use a fully charged jumper pack (not connected to AC outlet) as a supplemental source. *Important: *The ignition switch must be in the proper position. The Tech 2® will prompt you to turn the ignition ON, with the engine OFF. DO NOT change the position of the ignition switch during the programming procedure unless instructed to do so.

*Important: *If you experience programming issues utilizing the Pass-Thru method, please reattempt using the remote method with the Tech 2® and a "CANDi" module. If you are still experiencing programming issues, please call the Techline Customer Support Center for assistance.

An updated PCM calibration is now available to address this concern. This calibration, or any that follow, is designed to address this concern. Reprogram the PCM with the software now available in TIS2WEB using the Service Programming System (SPS). Use data version 2.5 for 2007 or later, available on TIS2WEB (website version of TIS) February 18, 2007; and on TIS DVD version 3.0 / 2007 or later, mailed to dealers beginning March 14, 2007.

If you cannot access the calibration, call the Techline Customer Support Center at 1-800-828-6860 (English) or 1-800-503-3222 (French) and it will be provided. As always, make sure your Tech 2® Diagnostic Scan Tool is updated with the latest software version.

*Important: *DTCs may be set during programming and additional reprogramming time is required for downloading the operation files with the calibration files.

Clear any codes and verify the condition has been fixed.

*Warranty Information*

<http://service.gm.com/servlets/BlobShtml?ShtmlFile=1912687&pubid=1647&evc=sm#ss4-1912687>For vehicles repaired under the 8 year/80,000 mile (130,000 kilometer) emission controller warranty, use:

Labor Operation

Description

Labor Time

J7915*

Reprogram Powertrain Control Module (PCM)

0.8 hr

*This is a unique labor operation for bulletin use only. This number will not be published in the Labor Time Guide.

corneredge · January 11, 2008

Thanks for posting the article, but my truck was delivered and has the latest software. The dealer has my truck now and same story... No misfire codes in the computer, no errors in the computer, so they won't do anything about it.

I'm very frustrated. I'm going to ask them what the vacuum numbers were to see if they even bothered to check.

at 3000 miles my truck

- idles terribly, misses repeatedly...feels like the back two cylinders fire ever other time.

- at RPM's less than 1700 or so, when I lean into the throttle the truck misses, which causes bad shifts occasionally.

- Sometimes it misses hard enough that it feels like you are being hit from behind at red lights

I have a fully loaded, gorgeous suburban, and I have to deal with an engine that runs this bad?

The dealer is telling me its a "characteristic" of the engine. Yeah, a characteristic, and consitent desing flaw!

-Russ

HawkScot · January 11, 2008

I might have missed something but I thought that the variable valve timing (V V T) was only on the 6.2L and that the active fuel management (AFM) was available on the 5.3 and 6.0 engines.

The missing/cutout might be related to the AFM but I doubt that it is part of the VVT.

I would expect a code if there are excessive misfires. If the computer thinks things are okay, then maybe the computer needs resetting?? I wonder if it would make a difference if you disconnected the battery overnight and then reconnected and let it learn things again.

I was also told that the remote start has a special firing mode to warm the engine up faster (I don't notice a different sound or anything but read it online somewhere but have not confirmed)... do you use remote start?

corneredge · January 11, 2008

I might have missed something but I thought that the variable valve timing (V V T) was only on the 6.2L and that the active fuel management (AFM) was available on the 5.3 and 6.0 engines.

The missing/cutout might be related to the AFM but I doubt that it is part of the VVT.

I would expect a code if there are excessive misfires. If the computer thinks things are okay, then maybe the computer needs resetting?? I wonder if it would make a difference if you disconnected the battery overnight and then reconnected and let it learn things again.

I was also told that the remote start has a special firing mode to warm the engine up faster (I don't notice a different sound or anything but read it online somewhere but have not confirmed)... do you use remote start?

Thanks Hawkeye, the 2008 chevy 6.0L has VVT and AFM. its the 366hp engine. (L76) Vortec 6.0L VVT V8 SFI - RPO Code - LY6

HawkScot · January 11, 2008

good to know! thanks, I learn something everyday on this forum...

GMTRUCKTECH · January 11, 2008

My brand new 6.0L suburban engine is running terribly. At idle it misses bad enough that you can feel it shaking the truck. At part throttle on the road I can feel it miss. Often when I lean into the throttle for a downshift, it misses before/during the shift and the trans shifts harder/bad.

Recently I also get a vibration over 50mph whenever the engine goes into V4 mode.

My dealer on first visit about it right after I picked up the truck insists "there is no problem" because there are no error codes in the computer. I'm going to go back to him again tomorrow.

I've had the truck for 2-3 weeks, I have 1000 miles on it. What do you recommend I ask for next? A compression test? I feel like I have a bad engine with a cylinder that's not up to snuff.

Thanks for the advice, a new engine with VVT should not idle or run this bad.

-Russ

If your truck is missfiring as bad as you say it would certainly set a missfire code or show missfires on each cyn with tech-2 data. Anyways here is a bull on rough idle and other driveability concerns see if your local dealer will perform this bull it MAY help.

Subject:Various Driveability Symptoms Due to Clogged Fuel Injectors, MIL/SES DTCs P0171, P0172, P0174, P0300, P1174, P1175 (Clean Fuel Injectors and/or Perform Injector Test With AFIT - CH-47976) #03-06-04-030F - (12/10/2007)

Models: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

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).

Condition

Some customers may comment on any of the following various driveability symptoms:

• Extended Crank Time

• Hard to Start

• MIL/SES Illuminated with DTCs

• Hesitation

• Lack of Power

• Surge or Chuggle

• Rough Idle

• Light or Intermittent Misfire

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. As a long term solution, and to prevent reoccurrence, customers should be encouraged to use Top Tier Detergent Gasoline . For further information on Top Tier detergent gasoline and fuel retailers, please refer to the following Corporate Bulletin Numbers:

• 04-06-04-047G (U.S. Only)

• 05-06-04-022D (Canada ONLY)

Notice: 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.

Injector Cleaning Procedure

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)

Active Fuel Injector Tester (AFIT- CH-47976)

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.

Training (U.S.)

To access the training video on AFIT, take the following path at the GM Training Website:

<LI type=1>After logging into the gmtraining.com website, choose the link on the left side of the page titled "web video library." <LI type=1>Then choose "technical." <LI type=1>Next, within the search box, type in September course number "10206.09D. <LI type=1>This will bring up a link with this course. Scroll through to choose "feature topic."
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 http://www.gmde.net/AFIT.cfm.

Training (Canada)

To access the training video on AFIT, take the following path at the GMPro LMS Training Website:

<LI type=1>After logging into the <www.gmprocanada.com> website, choose the link on the left side of the page titled "Catalog." <LI type=1>Then choose "Catalog Search." <LI type=1>Next, within the search box, Select Course Number - Contains - "T" then select search. <LI type=1>This will bring up a list of TECHassist courses. Scroll through to choose "Active Fuel Injector Tester" and select "View."
At this point, a new window will open and the program can be Launched.

Also, dealers can now download software updates for the AFIT at GM Dealer Equipment (GMDE) on the web at http://www.gmde.net/softwareupdates/.

Techlink

Additional information can be found on AFIT (June 2006 Edition) and GM Upper Engine and Fuel Injector Cleaner (November 2006 Edition) in Techlink. To access the articles, take the following path:

<LI type=1>Go to GM DealerWorld (U.S.) or the GM infoNET (Canada). <LI type=1>Click on the Service Tab in DealerWorld (GM infoNET for Canada). <LI type=1>Click on the GM Techlink Hyperlink.
Click on the Archives Hyperlink at GM Techlink.
• Click on 06-2006 in the Archives Section and Click on the Active Fuel Injector Tester Link in the June 2006 Techlink Article.

• Click on 11-2006 in the Archives Section and Click on the GM Top Engine Cleaner Replaced Link in the November 2006 Techlink Article.

Injector Cleaning Procedure

Notice: GM UPPER ENGINE AND FUEL INJECTOR 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 Upper Engine and Fuel Injector Cleaner be added to the vehicle fuel tank.

Do not exceed the recommended cleaning solution concentration. Testing has demonstrated that exceeding the recommended cleaning solution concentration does not improve the effectiveness of this procedure.

Important: Vehicles with less than 160 km (100 mi) on the odometer should not have the injectors cleaned. These vehicles should have any out of specification injectors replaced.

<LI type=1>For 4, 5 and 6 cylinder engines, empty two of the 30 ml (1 oz) reservoirs of the GM Upper Engine and Fuel Injector Cleaner container into the J 35800-A - Injector Cleaning Tank then add 420 ml (14 oz) of regular unleaded gasoline. If you are using any other brand of cleaning tank, you will need a total of 60 ml (2 oz) mixed with 420 ml (14 oz) of regular unleaded gasoline. <LI type=1>For 8 cylinder engines, empty two of the 30 ml (1 oz) reservoirs of the GM Upper Engine and Fuel Injector Cleaner container into the J 35800-A - Injector Cleaning Tank then add 420 ml (14 oz) of regular unleaded gasoline. If you are using any other brand of cleaning tank, you will need a total of 60 ml (2 oz) of Upper Engine and Fuel Injector Cleaner mixed with 420 ml (14 oz) of regular unleaded gasoline. This procedure will need to be repeated for a second time for an 8 cylinder engine (8 cylinder engines receive 960 ml total fluid - 120 ml (4 oz) of Upper Engine and Fuel Injector Cleaner and 840 ml (28 oz) of gasoline. <LI type=1>Be sure to follow all additional instructions provided with the tool. <LI type=1>Electrically disable the vehicle fuel pump by either removing the fuel pump fuse or the fuel pump relay and disconnecting the oil pressure switch connector, if equipped. <LI type=1>Turn the ignition to the OFF position. <LI type=1>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 42873 or J 42964 as appropriate for the fuel system. <LI type=1>Connect the J 35800-A to the vehicle fuel rail. <LI type=1>Pressurize the J 35800-A to 510 kPa (75 psi). <LI type=1>Start and idle the engine until it stalls, due to lack of fuel. This should take approximately 15-20 minutes. <LI type=1>Turn the ignition to the OFF position. <LI type=1>Disconnect the J 35800-A from the fuel rail. <LI type=1>Reconnect the vehicle fuel pump relay and oil pressure switch connector, if equipped. <LI type=1>Remove the J 37287, J 42873 or J 42964 and reconnect the vehicle fuel feed and return lines. <LI type=1>Start and idle the vehicle for an additional two minutes to ensure residual injector cleaner is flushed from the fuel rail and fuel lines. <LI type=1>Pour the entire contents of GM Fuel System Treatment Plus (P/N 88861011 [in Canada, P/N 88861012]) into the tank and advise the customer to fill the tank. <LI type=1>Review the benefits of using Top Tier Detergent gasoline with the customer and recommend that they add a bottle of GM Fuel System Treatment Plus to the fuel tank at every oil change. Regular use of GM Fuel System Treatment Plus should keep the customer from having to repeat the injector cleaning procedure.
Road test the vehicle to verify that the customer concern has been corrected.

Parts Information

Part Number

Description

Qty

88861802

GM Upper Engine and Fuel Injector Cleaner 473 ml (16 oz) Container (U.S.)

1*

88861804

GM Upper Engine and Fuel Injector Cleaner 473 ml Container (Canada)

1

88861011

Fuel System Treatment Plus 591 ml (20 oz) Container (U.S.)

1

88861012

Fuel System Treatment Plus 591 ml Container (Canada)

1

* Only 1/8 of the cost may be claimed for 4 and 6 cylinder engines and 1/4 of the cost for 8 cylinder engines.

Warranty Information (excluding Saab U.S. Models)

For vehicles repaired under warranty, use:

Labor Operation

Description

Labor Time

*J5645

Cleaning Injector:

4 Cylinder Engine

0.8 hr

5 Cylinder Engine

0.7 hr

6 Cylinder Engine

0.7 hr

8 Cylinder Engine

0.9 hr

**Add:

Diagnostic Time

0.0-0.3 hr

* This labor operation number is for bulletin use only. This number will not be published in the Labor Time Guide.

**A total diagnostic time equal to the time allowed for cleaning, J5645, may be claimed for performing the injector diagnosis procedure.

Warranty Information (Saab U.S. Models)

For vehicles repaired under warranty, use:

Labor Operation

Description

Failed Object

Fault/Reason Code

Location Code

Warranty Type

Repair/Action Code

Labor Time

2421101

Injector, Replace Engine Code S

24211

71

0

01

Use Published Labor Operation Time

2421102

Injector, Replace Engine Code M

24211

71

0

01

Use Published Labor Operation Time

Add

1002001

Diagnostic Time

--

Use Published Labor Operation Time

2421105

Cleaning Injector, 6 Cylinder Engine

24211

71

0

01

05

0.7 hr*

2421106

Cleaning Injector, 8 Cylinder Engine

24211

71

0

01

05

0.9 hr*

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.

WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION

Document ID# 2043811

2008 Chevrolet Chevy Suburban - 2WD

corneredge · January 11, 2008

Thanks for the bulletin. My dealer just informed me there is nothing they can do. All the techs that drove my truck, includin gthe service mgr insist that the truck drives "normal". Nothing "that is not a characteristic of that engine" is happening.

Do 6L Corvettes have rough idles too?

-Russ

Kanima · January 11, 2008

Take it to another dealer, Mine downloaded EVERYTHING there was out there on the 6.0l and 07's + to mine computer yesterday..

And it fixed my s**tty idle and my missing at highway speeds.

Hell tell them where they can feel it or not, the truck is under warrenty and what can it hurt to update the PCM ??

Kanima · January 11, 2008

I'd also question the fact it has the newest software unless they ( the dealer) put it on there my is an 08 and it still had 07's software.

corneredge · January 11, 2008

From what I undersant the GM PCM updates are cumulative, and I confirmed today my software is the latest. I'm going to try disconnecting the battery tonight to see if that does anything to help.

gmtech4 · January 12, 2008

From what I undersant the GM PCM updates are cumulative, and I confirmed today my software is the latest. I'm going to try disconnecting the battery tonight to see if that does anything to help.

hi ,holy cow.,you don't have to disconnect the batteries,if the dealer said it is normal,please ask them to prove it with a known good vehicle,off the lot ,go for a drive ,if its normal,eat crow I guess.go to where you bought/leased the "burb",gl .