Diagnosing and prep for harmonic balancer replacement 4.2 L I6

[pastorbud]

I’m looking at replacing the harmonic balancer on my 07 Envoy 2WD 4.2 I6. But before I go to tearing into all that and buying special tools, is there a way to diagnose if it actually is causing the problem I think it is? The problem is the engine vibrates at idle. It does it in neutral are in drive when idling at a stoplight or in the driveway. Goes away with RPM increase. It’s not even detectable when driving down the road. It’s not a real violent vibration just loud and annoying. It’s gone on for over a year.

I’ve replaced the idler pulleys, already has a new power steering pump (it was noisy). A mechanic friend said it was either the motor mount, or the harmonic balancer. I paid him to do the motor mounts…. Vibration endures.

I have the fan shroud off and just installed a new water pump. I was going to do the harmonic balancer while I was in there, but when I see the special tools and everything that is involved, I kind of wonder if there’s anything else I should check Before I pull the trigger on such a big job.

Is there a way to know for certain the balancer is the problem?

 

[azswiss]

I would start by checking to see if you have any misfires. Do you have access to a scan tool?

 

[pastorbud]

Yes, I have a scan tool. Easy to test. But wouldn’t I get an SES light if it were misfiring?

 

[pastorbud]

Plus it just passed CT emissions test. I’d expect that to flag a misfire.

 

[Mooseman]

Check your engine mounts. Classic vibration at idle or when stopped in the 50hz range.Replace only with ACDelco.

Unless your balancer is wobbling, it's not.likely the issue.

 

[pastorbud]

Check your engine mounts. Classic vibration at idle or when stopped in the 50hz range.Replace only with ACDelco.

Unless your balancer is wobbling, it's not.likely the issue.

Thanks already did the engine mounts. It’s a long post, but I mentioned that above. Also did just about everything else that hangs on the front of the engine 😳

 

[mrrsm]

You don't mention the Engine Mileage... but another source for Low RPM, Asymmetric Vibration (Rough Running Engine) on High Mileage Motors can come from Worn Main Bearings and the Thrust Bearings situated at a Right Angle to the Axis of Rotation involving the Two Babbitt Thrust Plates slipped alongside the #5 Mains Bearing Buttress.

In short... if the Bearings are worn out... as mentioned by @Mooseman ... replacing the Harmonic Balancer as a Low Failure, Massive Bi-Component System separated by an Elasto-Meric Binder would not necessarily solve this problem. It IS possible to measure the wear of the Thrust Bearings by attempting to take a longitudinal movement measurement with a Dial Bore Gauge reading the Flat Outer Surface of the Harmonic Balancer... Fore and Aft ... for Excessive End Play and following the comparison of Nominal OEM Factory Specs versus any Excessive End Play Measurement suggesting an impending Engine Failure:

THIS Information should prove useful... even though THIS relates to 2005-2006 Engines, but take note of the Highlighted Specifications below for reference to your situation.:

Subject: DTC P0014, P0017, and/or Belt Noise - Inspect Actuator Solenoid and Crank End Play - keywords bearing cam chirp damaged debris internal light metal P0106 Phaser replacement run SES squeak thrust #PIP3693B - (04/04/2006)

Models:2005-2006 Buick Rainier 2005-2006 Chevrolet TrailBlazer 2005-2006 GMC Envoy 2005-2006 Saab 9-7x with 4.2L Engine (VIN S - RPO LL8)

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

Condition/Concern:

On rare occasions, a rough idle may be encountered with a P0014 and/or P0017 DTC. Due to the rough idle, a P0106 DTC may be stored too. This concern may be due to debris in the camshaft actuator system, which may be caused by a missing camshaft actuator solenoid screen or a worn crankshaft thrust bearing. Typically, this is the result of a camshaft actuator solenoid concern. If this is due to a worn crankshaft thrust bearing, some customers may also comment on a drive belt noise.

Recommendation/Instructions:

If this concern is encountered, follow the SI diagnostics and repair as necessary. If the SI diagnostics do not isolate the cause of this concern, ensure that camshaft actuator solenoid screens 1, 2, and 3 are in place as shown below:

(1)Screen for Advance Pressure to Camshaft Actuator( 2) Screen for Pressurized Oil from Oil Pump(3)Screen for ****** Pressure to Camshaft Actuator If any of these screens are missing, replace the camshaft actuator solenoid, change the engine oil and filter, and evaluate the concern.

If all these screens are present, measure the crankshaft end play to determine if it is within the specification of 0.0044" - 0.0153" (0.112 - 0.388 mm). Typically, if excessive crankshaft end play is causing this concern, it will be obviously out of specification by .050" or more. If crankshaft end play is within specification, replace the camshaft actuator solenoid.

If the crankshaft end play is obviously out of specification, inspect the engine block for damage due to contact with the crankshaft. If engine block damage is present, contact the PQC (Product Quality Center) at 1-866-654-7654 for engine replacement authorization.

If there is no engine block damage present, disassemble the engine and inspect the following components for damage due to thrust bearing debris in the engine oil: all bearings, all journals, all valve-train components, all timing components, and the crankshaft

Then, estimate what it will cost to replace the oil pump, camshaft actuator solenoid, all damaged parts, and to completely disassemble the engine to thoroughly clean all of the cylinder head and engine block oil galleys with oil galley brushes and soapy water.

After the repair estimate is complete, estimate what it would cost to replace the engine and contact the PQC to review these estimates as outlined in 02-07-30-029F.

Important: On 2006 models with excessive crankshaft end play, please submit a field product report by following 02-00-89-002D.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

 

[pastorbud]

It is high mileage…going on 210k. So I should check for play, fore and aft, in the crankshaft? I guess I’d use a dial indicator and try to move the crankshaft forward with a pry bar?

 

[mrrsm]

No... according to the information in the Diagnostic Flow Chart mentioned above in the body of the TSB, the FIRST thing to investigate is to completely unbolt the Three Fasteners holding in the Power Steering Pump to move it clean (RTF) out of the way... and then unplug the Harness Connector and unfasten the Bracket Bolt on the CPAS (Camshaft Position Actuator Solenoid).

Then... pull it out of the upper front Passenger Side of the Engine Head. Then... inspect the Three Oil Filter Screens in the body of the CPAS for any that are Clogged Up or MISSING that may have come loose and then become ingested into the Helical Gears hidden inside of of your Old Style Exhaust Camshaft Phaser or gotten flushed out into the Oil Flow and carried down into the Crank-Case.

If the Screens are absurdly Clogged Up with Debris ...or completely gone... read more above in the TSB about obtaining a Quality Replacement CPAS and be certain to change the Motor Oil and Filter at the same time before starting the Engine. Hopefully ...this will have a decidedly beneficial effect and the Vibrations will subside. Having to carefully measure the vagaries of "Crankshaft End Play" using a Dial Indicator upon a Fully Dressed LL8 4.2L Motor is NOT a trivial matter and should follow on only if absolutely necessary.

Look for the CPAS R&R Instructions in the GMTN FAQ ( I could NOT locate a Link to it) . In addition to what has already been written ... I have found there are many Videos like the one below available on YouTube that give Folks the chance to "Take A Peek over the Mechanic's Shoulder" and see how all of this work gets done... without skipping any steps or missing anything important:

Visit THIS Link at RockAuto (a Preferred Vendor) and decide which CPAS to buy if cost on parts is an issue:

2002 CHEVROLET TRAILBLAZER 4.2L L6 Variable Valve Timing (VVT) Solenoid / Actuator | RockAuto

RockAuto ships auto parts and body parts from over 300 manufacturers to customers' doors worldwide, all at warehouse prices. Easy to use parts catalog.

www.rockauto.com

THIS is the OEM Part that you should prefer over all others (I'm VERY Surprised to see that the ACDelco Component is still available over on Amazon). Take Note of the presence of the Three Screens in these OEM Images having a modification of Wound Wire Spring Coils encircling them to prevent their ejection (or ingestion) from within the CPAS device. Factor in your S&H costs between these two Vendors before you "Pull the Pin" and make the purchase.

https://www.amazon.com/dp/B01K8DRWHM/?tag=gmtnation-20

 

[pastorbud]

Oh yeah that thing. I had to do that on my 2002 Envoy (since deceased). I forgot all about it. Pesky little critter. Not sure if I’ll get to that today. Thanks.

 

[Mooseman]

What brand mounts did the mechanic install? Anything but OEM is hit or miss as the originals were hydraulic and the aftermarket don't always get it right.

Another possibility is a dirty throttle body. Clean it using these instructions:
How to clean your throttle body

Of importance while doing this is either disconnecting the battery or pulling the two PCM fuses to reset the PCM.

 

[TJBaker57]

Since no one else mentioned it (or I missed it) I will point put that replacing the harmonic balancer will also require a Crankshaft Position Variation Learn procedure. This will require a dealership level scantool.

 

[pastorbud]

No... according to the information in the Diagnostic Flow Chart mentioned above in the body of the TSB, the FIRST thing to investigate is to completely unbolt the Three Fasteners holding in the Power Steering Pump to move it clean out of the way... and then unplug the Harness Connector and unfasten the Bracket Bolt on the CPAS (Camshaft Position Actuator Solenoid).

Then... pull it out of the upper front Passenger Side of the Engine Head. Then... inspect the Three Oil Filter Screens in the body of the CPAS for any that are MISSING that may have come loose and become ingested into the Helical Gears hidden inside of of your Old Style Exhaust Camshaft Phaser or gotten flushed out into the Oil and down into the Crank-Case.

If the Screens are absurdly Clogged Up with Debris ...or completely gone... read more above in the TSB about obtaining a Quality Replacement CPAS and be certain to change the Motor Oil and Filter at the same time before starting the Engine. Hopefully ...this will have a decidedly beneficial effect and the Vibrations will subside. Having to carefully measure the vagaries of "Crankshaft End Play" using a Dial Indicator upon a Fully Dressed LL8 4.2L Motor is NOT a trivial matter and should follow on only if absolutely necessary.

Look for the CPAS R&R Instructions in the GMTN FAQ ( I could NOT locate a Link to it) . In addition to what has already been written ... I have found there are many Videos like the one below available on YouTube that give Folks the chance to "Take A Peek over the Mechanic's Shoulder" and see how all of this work gets done... without skipping any steps or missing anything important:

Visit THIS Link at RockAuto (a Preferred Vendor) and decide which CPAS to buy if cost on parts is an issue:

2002 CHEVROLET TRAILBLAZER 4.2L L6 Variable Valve Timing (VVT) Solenoid / Actuator | RockAuto

RockAuto ships auto parts and body parts from over 300 manufacturers to customers' doors worldwide, all at warehouse prices. Easy to use parts catalog.

www.rockauto.com

THIS is the OEM Part that you should prefer over all others (I'm VERY Surprised to see that the ACDelco Component is still available over on Amazon). Take Note of the presence of the Three Screens in these OEM Images having a modification of Wound Wire Spring Coils encircling them to prevent their ejection (or ingestion) from within the CPAS device. Factor in your S&H costs between these two Vendors before you "Pull the Pin" and make the purchase.

https://www.amazon.com/dp/B01K8DRWHM/?tag=gmtnation-20

View attachment 107662View attachment 107663View attachment 107664

Well, I did get to it after all. CPAS screens were intact and free of debris. But the CPAS was old and did not have the coil spring around the screens. So I replaced it with a new one. Sadly not OEM, since I had to have it back together to drive it to work tomorrow.

But… the problem endures. Replacing CPAS did not fix it.

 

[pastorbud]

Since no one else mentioned it (or I missed it) I will point put that replacing the harmonic balancer will also require a Crankshaft Position Variation Learn procedure. This will require a dealership level scantool.

Yikes. Definitely a last resort.

 

[pastorbud]

What brand mounts did the mechanic install? Anything but OEM is hit or miss as the originals were hydraulic and the aftermarket don't always get it right.

Another possibility is a dirty throttle body. Clean it using these instructions:
How to clean your throttle body

Of importance while doing this is either disconnecting the battery or pulling the two PCM fuses to reset the PCM.

Thanks. Worth a shot.

 

[pastorbud]

I’m going to post a video of what it’s doing. It doesn’t consistently idle rough. It kinda bogs down and gets rough, almost like when you first engage the clutch on a manual tranny (it’s not a manual). Will try to make video of it tomorrow. Hopefully you can hear the vibration and see the rpm go down on the video. Maybe I could put a scanner on it and watch the readings from various sensors to get some idea of what is causing this? My scanner can export a record of the readings to Excel.

 

[Mooseman]

Since no one else mentioned it (or I missed it) I will point put that replacing the harmonic balancer will also require a Crankshaft Position Variation Learn procedure. This will require a dealership level scantool.

First time I've heard of this one.

 

[TJBaker57]

First time I've heard of this one.

Commonly called a CASE learn, the Tech II calls it this...

 

[Mooseman]

I mean first time I've heard of it required with a balancer replacement.

 

[TJBaker57]

I mean first time I've heard of it required with a balancer replacement.

 

[Mooseman]

Learn something every day. Maybe not necessary if you don't get a code or CEL for it. I'd let it ride (and have in the past)

 

[pastorbud]

Here’s the video. That plastic tapping sound at the end is just my cheap phone holder 😜

Idling

I’m starting to wonder if I’ve been chasing mechanical problems when it’s actually a sensor or control problem. Could I monitor it live with a scanner and watch for what is reducing RPM? What is normal RPM at idle?

 

[pastorbud]

Here’s the video. Posted twice somehow. That plastic tapping noise is just my cheap phone holder.

I’m starting to wonder if I’ve been chasing mechanical problems when it’s actually a sensor or control problem. Could I monitor it live with a scanner and watch for what is reducing RPM? What is normal RPM at idle?

 

[pastorbud]

The sound quality is pretty bad on that YouTube video. It doesn’t make that loud clicking noise. It just slows down and starts to vibrate at about 600 RPM.

 

[mrrsm]

Try removing the Serpentine Belt and then Starting the Engine (VERY Briefly) and listen-feel for the Low Idle Vibration. If it subsides, then suspect something in the Water Pump Bearings-Fan-Shroud relationship. Inspect the Serpentine Belt for any signs that any excess Longitudinal End Play is forcing the Belt Ribs to move laterally...and cause it to Fray along ts edges. If nothing else, this Test might eliminate suspicion about the other accessories being involved; such as having a Worn Out Idler Pulley Bearing or a Weak Belt Tensioner... or even from using a Serpentine Belt that is either TOO Long or TOO Short by even a Fraction of the acceptable OEM Belt Length.

 

[Mooseman]

I didn't see it go down to 500. 630-650 is normal idle. For erratic idle, we usually recommend to clean the throttle body as per these instructions:

How to clean your throttle body

 

[pastorbud]

Try removing the Serpentine Belt and then Starting the Engine (VERY Briefly) and listen-feel for the Low Idle Vibration. If it subsides, then suspect something in the Water Pump Bearings-Fan-Shroud relationship. Inspect the Serpentine Belt for any signs that any excess Longitudinal End Play is forcing the Belt Ribs to move laterally...and cause it to Fray along ts edges. If nothing else, this Test might eliminate suspicion about the other accessories being involved; such as having a Worn Out Idler Pulley Bearing or a Weak Belt Tensioner... or even from using a Serpentine Belt that is either TOO Long or TOO Short by even a Fraction of the acceptable OEM Belt Length.

 

[pastorbud]

Thanks to everybody. I’m gonna be on the road for the next eight or nine days I won’t have time to work on this for a while. I’ll probably do the throttlebody first because at 210,000 miles, It probably needs it regardless. If That doesn’t do it I’ll do the serpentine belt thing… I had heard about that technique before, but I’ve always been afraid to try it!😜

 

[adam.nees26]

Thanks to everybody. I’m gonna be on the road for the next eight or nine days I won’t have time to work on this for a while. I’ll probably do the throttlebody first because at 210,000 miles, It probably needs it regardless. If That doesn’t do it I’ll do the serpentine belt thing… I had heard about that technique before, but I’ve always been afraid to try it!😜

Did you ever find a fix here? Seems like I’m going through the same

 

[mrrsm]

Some additional information for the OP regarding WHY the vibration disappears at 800 RPM versus its return whenever idling the Engine:

(1) When Idling at around 600 RPM... The Idle Air Control of the TAC Unit handles the need to keep the dynamics of having a minimal amount of stress on the Engine Internal Rotating Assembly necessary to keep the Engine running. However... as soon as you "Step On The Gas"... (ACC Pedal) whatever "slack" or relaxed looseness that Worn Connecting Rod Bearings and Worn Main Bearings can experience to invite Low Idle Internal Engine Vibrations is literally "Taken OUT" after the additional Demand for Power increases as the RPM and Torque rises, forcing all of these components closer together rotationally while under harder acceleration.

(2) At the lower Idle Speed of 600 RPM, The Gerotor Oil Pump is producing Less Oil Pressure and thus, it can allow for a decrease in the Oil Volume present within the spaces around the Worn Connecting Rod and Worn Crankshaft Bearings... as another invitation to excess vibration that will disappear as soon as the Oil Pressure pushes a greater volume of Oil into those spaces at 800 RPM. Nominal Oil Pressure for the GM Atlas LL8 4.2L Engine is 12 PSI at a Minimum which can be expected at or near Idle... and it increases to around 65 PSI from 3,000 RPM in the Mid to Upper Range Power Band.

When unmodified by having a Special Woodruff Key for a High Performance Harmonic Balancer machined into the nose of the GM OEM Crankshaft, the ordinary Redline for this Motor is 6,500 RPM. Any amount of Engine RPM that raises the Gerotor Oil Pumping Pressure above 65 PSI is soon bled off by a Spring Loaded Relief Valve inside that unit that will dump off the excess oil back into the Crankcase. There is a second By-Pass Oil Pressure Valve in the Oil Filter Manifold designed to prevent the Thin Steel Shell of the Oil Filter Canister from bursting under excessive hydraulic pressure.