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'14 1500 4.3 shaking in V4 mode


Darel Matthews

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Repost from the general troubleshooting board, they recommended I come over here...

 

2014 LT Z71 with 4.3.

 

When the cylinder deactivation kicks in and the truck switches into V4 mode, it has a very noticeable vibration or shake.  Not unlike driving on a washboard road.  This is not a wheel balance / driveline issue, it's definitely when the cylinders are deactivated and it's pretty much like a light switch.  Anytime, any speed, the truck is in V4 it's shaking.  Engine is totally smooth in V6 mode with all cylinders firing.

 

The shaking occurs the entire time the truck is running in V4 mode, NOT as it transitions in and out of it (as most of the other guys seem to have indicated).  The entire time the truck is in V4 mode, it feels like it's driving on a washboard road at all speeds and under all driving conditions.  V6 is perfect.

 

DIsclaimer: I "inherited" the truck from my dad, who swears it never had any vibration, but I felt it driving the truck home from his house for the first time.  My dad also doesn't know how to put gas in his own car, and is the sort of person who goes into a dealership and says, "I would like one car, please."

 

Thanks,

Darel

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Sounds to me like one of the AFM lifters have failed. I'm not familiar with the V6 AFM system, but I'm certain it's the same failure prone crap from the V8's. There's also the possibility that it's overdue for an oil change, and/or the wrong oil was used, the VLOM (valve lifter oil manifold) failed, or there's an electrical issue that's not allowing oil to the lifter when commanded. 

 

Usually they fail unlocked, where there's a constant misfire at all times. Sounds like these have failed in the locked position. That's new to me, but this is good news for you - I would just buy a Range AFM Disabler, plug it in to your data link connector (where scan tools plug in) under the dash, and go about life normally with a normal V6. That would be your cheapest possible option.

 

EDIT: I may have the locked vs. unlocked symptoms backwards. Stupid system! I can't keep GM's engineering straight, and neither can they ...

 

I don't have any experience with '13-up models, so GM could have changed something in the lifter's design from the prior generation, but didn't fix the problem, of course - I expect nothing less.

Edited by Jsdirt
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disregard ...

Edited by Jsdirt
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Thanks.  I'm not interested in masking a problem, so I'll fix it one way or another...besides I like the gas mileage I get and my '07 with AFM has been flawless for 200,000 miles now.  I'll start out with an oil change and see how things progress.

 

Anyone know anything about some sort of exhaust damper the dealers were trying a while back?

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You won't notice a difference in mileage. I've been running mine for 40k+ miles and mileage is exactly the same. Of course, if you run it in AFM mode alot, then maybe you will.

 

I'm amazed you got that many miles before failure. Guess they tried to improve the design, but, fell short as usual. The V8's of the earlier gen failed between 90k-130k miles. I'm waiting for mine to check out at 113k now ...

 

Just be prepared - you're going to have a big bill to fix this if it is the lifters that failed. The way they designed these engines requires ALOT of labor to access them.

Edited by Jsdirt
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Yeah the '07 is around 200k and no issues at all (other than the rear fenders falling off).  The '14 only has 40k and shakes like a leaf.  Supposedly the earlier GMT900s were fine (like mine) but then they changed something that kinda ruined the system. I had a boss with a '13 that burned 2 quarts every 500 miles until he programmed it out.  

 

 

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3 hours ago, Darel Matthews said:

Repost from the general troubleshooting board, they recommended I come over here...

 

2014 LT Z71 with 4.3.

 

When the cylinder deactivation kicks in and the truck switches into V4 mode, it has a very noticeable vibration or shake.  Not unlike driving on a washboard road.  This is not a wheel balance / driveline issue, it's definitely when the cylinders are deactivated and it's pretty much like a light switch.  Anytime, any speed, the truck is in V4 it's shaking.  Engine is totally smooth in V6 mode with all cylinders firing.

 

The shaking occurs the entire time the truck is running in V4 mode, NOT as it transitions in and out of it (as most of the other guys seem to have indicated).  The entire time the truck is in V4 mode, it feels like it's driving on a washboard road at all speeds and under all driving conditions.  V6 is perfect.

 

DIsclaimer: I "inherited" the truck from my dad, who swears it never had any vibration, but I felt it driving the truck home from his house for the first time.  My dad also doesn't know how to put gas in his own car, and is the sort of person who goes into a dealership and says, "I would like one car, please."

 

Thanks,

Darel

 

 

Does it occur at 1200-1400rpm so lets say at low speeds, and then say 45-50mph?

 

If so expand and read below:

 

Quote

 

#PIP5228D: Vibration During Active Fuel Management V4 Mode Operation 1200 – 1400 Engine RPM - (Mar 16, 2017)

Subject: Vibration During Active Fuel Management V4 Mode Operation 1200 – 1400 Engine RPM

 

Chevrolet

Silverado

2014-2017

4.3L LV3

 

GMC

Sierra

2014-2017

4.3L LV3

 

Supersession Statement

This PI was superseded to update Parts and Warranty. Please discard PIP5228B.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

 

Condition/Concern

Some customers may comment about a vibration that is felt between 1200 – 1400 engine RPM when in active fuel management V4 mode.

 

A drone or resonance may also accompany this vibration.

The vibration may occur at different vehicle speeds but the engine speed will be in the 1200-1400 RPM range.

This vibration does not occur in V6 mode

 

Recommendation/Instructions

The technician should evaluate the vehicle under the conditions the customer duplicates the concern. Once the concern is duplicated, use vibration analysis tool CH 51450-NVH Pico Oscilloscope Diagnostic Kit (w/NVH) to measure the frequency of the vibration. If the measured vibration is not 21-25 Hertz (HZ), first order engine, use normal vibration diagnostics to isolate the source of the vibration.  If the measured vibration is 21-25 Hertz (HZ), first order engine, install the exhaust damper per the instructions below. If this does not reduce the vibration, follow the three-way catalytic converter and cab mount settling procedures below.

 

Install Exhaust Damper

Installation of an exhaust damper reduces the exhaust vibrations associated when the engine changes from V6 to V4 mode during AFM (Active Fuel Management). Installation location and position is critical to the performance of the damper.

 

The damper will be located on the passenger side exhaust pipe, directly above the transmission cross member.  It should be located on the inboard side of the exhaust directly in front of the resonator. It should be mounted so that the damper is horizontal with the clamp positioned as shone in the pictures below. 

Important: The exhaust clamp should be positioned so that is will not contact the heat shield above or the frame rail below.


Three-Way Catalytic Converter Assembly Settling Procedure

Note: Do NOT replace the three-way catalytic converter assembly unless it is physically damaged.

Loosen the six nuts that fasten the three-way catalytic converter assembly to the exhaust manifolds.

Remove and replace the exhaust muffler clamp that joins the three-way catalytic converter assembly to the pipe of the muffler assembly.  

 

Note: This is a special clamp called a Norma clamp and it must be replaced as it is a one time use clamp.

Reinstall the three-way catalytic converter assembly following the specific tightening sequence and fastener torque specifications found in SI.

 

Cab Mount Settling Procedure

Warning: When settling the body cushions, do NOT separate the frame from the body more than is necessary. Possible personal injury and damage to multiple parts may result if you do not follow the guides outlined below:

Intermediate steering shaft—Do not allow the shaft to extend more than 25 mm (1 in).

Fuel tank filler hose—Do not stretch the hose excessively.

Tail/Turn signal lamp wiring/rear lamps junction block—Leave slack in the wires

Park brake cable—Leave slack in the cable.

Body ground straps—Leave slack in the wire.>>>>>

The technician should first loosen the fastener located at the center of each body mount (6 for a regular cab, 8 for crew and double cab).

Using a large angled pry bar, lift up the cab body slightly to settle / relax it. Perform this at each mount location one at a time.

Repeat this cab mount settling process twice, to confirm the mounts are settled / relaxed.

Visually verify that the cab to box alignment is correct before re-torqueing  all mounts to specification found in Service Information, body repair, frame and under body section.

The cab / body mount position locations

The numbers in the picture below indicate the specific mount position.  The mounts on the passenger side of the vehicle are identified the same way. This will assist the technician to identify the correct location of each mount so they can be torque to the proper specification.

 

 

 

In short, loosen and re-set the cat Y pipe and install a vibration damper on the end of the Y pipe, maybe check the cab mounts.  

Edited by newdude
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That would be nice if that's what it is. Cheap and easy - can do that yourself in the driveway.

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Thanks, I had found this bulletin before, but it doesn't list a part number for the dampener.  Do you happen to know what it is?  Also looking on sites like GMPartsdirect doesn't show anything in the explodeds.

 

It does it all the time, 100% of the time every time in AFM, regardless of engine or road speed.  V4 = shake, V6 = no shake.  

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17 minutes ago, Jsdirt said:

You won't notice a difference in mileage. I've been running mine for 40k+ miles and mileage is exactly the same. Of course, if you run it in AFM mode alot, then maybe you will.

 

I'm amazed you got that many miles before failure. Guess they tried to improve the design, but, fell short as usual. The V8's of the earlier gen failed between 90k-130k miles. I'm waiting for mine to check out at 113k now ...

 

Just be prepared - you're going to have a big bill to fix this if it is the lifters that failed. The way they designed these engines requires ALOT of labor to access them.

 

Huh? So much unbacked up assumptions. So if a small percentage of trucks have AFM issues they all do regardless of the years and it sounds like you say they all fail before 130k or it is an anomality if they don't? Then you go on to say it won't change your gas mileage unless it is running in 4 cylinder mode which is exactly when it saves fuel and raises your gas mileage...Shesh, so basically it works as advertised and as independent testing has showed saves fuel and it has a low failure rate which is on par with anything that built by humans and machines made up of thousands of parts sold in mass quantities. Thanks! We got some good unbiased info there! 

 

We understand some people get burned by a failure or don't like something new such as AFM, a turbo four cylinder or auto start stop; but then they have to come in every thread and talk about how bad they think it is in their eyes which doesn't help and is completely unrealistic from reality. 

 

Tyler

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16 minutes ago, Darel Matthews said:

Thanks, I had found this bulletin before, but it doesn't list a part number for the dampener.  Do you happen to know what it is?  Also looking on sites like GMPartsdirect doesn't show anything in the explodeds.

 

It does it all the time, 100% of the time every time in AFM, regardless of engine or road speed.  V4 = shake, V6 = no shake.  

 

 

84090482

Exhaust Damper

 

15748648

Exhaust Clamp

 

20779889

Clamp, Exhaust Pipe

 

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11 hours ago, Amcguy1970 said:

 

Huh? So much unbacked up assumptions. So if a small percentage of trucks have AFM issues they all do regardless of the years and it sounds like you say they all fail before 130k or it is an anomality if they don't? Then you go on to say it won't change your gas mileage unless it is running in 4 cylinder mode which is exactly when it saves fuel and raises your gas mileage...Shesh, so basically it works as advertised and as independent testing has showed saves fuel and it has a low failure rate which is on par with anything that built by humans and machines made up of thousands of parts sold in mass quantities. Thanks! We got some good unbiased info there! 

 

We understand some people get burned by a failure or don't like something new such as AFM, a turbo four cylinder or auto start stop; but then they have to come in every thread and talk about how bad they think it is in their eyes which doesn't help and is completely unrealistic from reality. 

 

Tyler

Just telling like I see it. This is what I see. Since you have all the answers, why aren't you helping people in this forum? Why do I seem to be the only one that attempts to help people in here?

 

I saw ZERO fuel mileage change with AFM disabled. So ... you're going to tell  me I'm wrong? LOL! You're pretty f'in funny. 

Edited by Jsdirt
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144,000 on my 2015 V6 and AFM has been running flawlessly and seamlessly the entire time. Mook keeps telling me it's going to blow any day now. He could be right. 

 

Best I can calculate in A-B-A-B test is it is good for about a 6-8% boost in mileage when operated under the most efficient conditions. Adds nothing when operated outside it range thus either off or only on when fuel trim is maxed out...like coasting down hill at 80 mph. Would appear the SAE agrees...link to Tech Paper below:

 

https://19january2017snapshot.epa.gov/sites/production/files/2016-10/documents/2016-01-0662-fuel-eff-map-2014-6cyl-gm-eco-tec-4.3l-eng-cyl-deac_0.pdf

 

I looked this up once and @newdude will correct me if I error on this but I recall the lifters/guides/VLOM remain the same as the pre 2014???? At least they come up the same part number.

 

All that said JSDIrt's comment about failure:

 

19 hours ago, Jsdirt said:

The V8's of the earlier gen failed between 90k-130k miles.

 

 He provided both the context for his experience (above quote) and stood in awe of the accomplishment. (below)

 

19 hours ago, Jsdirt said:

I'm amazed you got that many miles before failure. Guess they tried to improve the design, but, fell short as usual.

 

We can afford to extend some grace, right?

 

As to his observed failure point...it actually makes sense. About how long it would take to varnish up the VLOM or screens OR add a thou or so wear to the lifter bores when the operator has not been diligent in oil maintenance either in frequency or selection. This was also the Melling observation; the manufacture of the OEM parts. 

 

https://www.melling.com/wp-content/uploads/2018/03/Melling-tech-bulletin-on-GM-LS-Deactivation-Lifter-Issues-3.1.18-1.pdf

 

 

 

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