AFM Lifter failure cause

pickmeup · March 1, 2019

On 2/10/2019 at 11:46 AM, Grumpy Bear said:

Between the Melling and the GM video's there is a ton of enlightening information. I took special note that both sources say the failure is caused by a 'mistimed' switching event. That is, switching, while off the base circle. Switching events on the ramps or nose 'bite' the pins while under load damaging the outer shell "shelf' locking it to the inner assembly. I also noticed that Melling, speaking of the LS motors ONLY specifies 27 psig as the minimum latching pressure while GM speaking of AFM in general specifies 22 psig as the minimum. Odd as they do not concern themselves until oil pressure drops to 19 psig hot idle.

So the question is what causes a 'mistimed' event? Pretty sure the ECU and the solenoids in the VLOM don't step out of time. Ones and Zeros and all. So it seems reasonable that plugged filters or restricted channels hinder rapid pressure up of the lifters taking longer to reach the 22/25 psi minimum. Time in a motor is degrees of rotation correct? It positional thus the ECU fires and the solenoids hit on time but the oil pressure rise time lags long enough for the cam to turn to the ramp or beyond. Ops, horse is out of the barn!

On point.

My question would be when stabiltrack takes over its many functions including reduced engine power in rapid sequences could that cause it to step out of sync.? Many report they get service stabiltrac light first and then 15 20 seconds later CEL light . Coincidence or is their more ? Melling article is very good read and can;t help what causes engines with 5 to 20,000 miles to fail. No way in hell is that sludge related .

Grumpy Bear · March 2, 2019

On ‎2‎/‎10‎/‎2019 at 9:19 AM, KARNUT said:

Hard to understand how sludge could be a problem with the temps these engines run and the types of oil that are available today. My brother in law routinely keeps his Tahoe 300K miles he's on number 4 and a high mileage p/u. He follows manufactures service schedule. He just got a 13 his first cylinder deactivation engine, this will be interesting. He only had one failure, a rear end went out on a suburban right at 300K a couple of rides ago.

This just sunk in. Why do we believe over temperature is the only thing that causes 'sludge'? Depleted TBN, water/fuel contamination and short tripping so that the oil never sees a hour in the fully warmed up conditions. Aeration and foaming.

BTW depleted TBN doesn't mean a zero TBN.

3 hours ago, pickmeup said:

My question would be when stabiltrack takes over its many functions including reduced engine power in rapid sequences could that cause it to step out of sync.? Many report they get service stabiltrac light first and then 15 20 seconds later CEL light . Coincidence or is their more ? Melling article is very good read and can;t help what causes engines with 5 to 20,000 miles to fail. No way in hell is that sludge related .

Did you notice close to the end of the video he mentions not just sludge but 'oil delivery' issues? Oil pump. VLOM solenoids, lifter bore tolerance...…. and yes, every once in a while a defect in materials, fit or finish.

Problem with this issue is the number of self inflicted wounds in rational thought. A butterfly in Indochina causes a hurricane in Cuba and the world demands an extinction event for all butterflies.

Had a few flat tires in my life. Should I go back to hard rubber hoops or wooden wheels?

Edited March 2, 2019 by Grumpy Bear

tbarn · March 2, 2019

Her is some info as to when AFM is activated. Use it for what you will.

To provide maximum fuel economy under light load driving conditions, the engine control module (ECM) will command the cylinder deactivation system ON to deactivate engine cylinders 1, 7, 6, and 4, switching to a V4 mode. The engine will operate on 8 cylinders, or V8 mode, during engine starting, engine idling, and medium to heavy throttle applications.

Manifold absolute pressure (MAP) and the conditions listed below determine when cylinder deactivation is enabled.

Engine has been running for greater than 30 s
Engine speed is between 700 and 2800 rpm
Engine oil pressure is between 187–455 kPa (27–66 psi)
Engine coolant temperature is between 40–129°C (100–264°F)
Engine oil temperature is between 16–128°C (61–263°F)
Throttle angle is 6% or less
Ignition voltage is greater than 11 V
Transmission is not in first, second, or reverse gear
Vehicle speed is greater than 25 kph (15.5 mph)
Brake booster pressure is greater than 42.0 kPa (6 psi)
Vehicle is not in fuel shut off mode
Vehicle is not in heater performance mode
Vehicle is not in tip in bump acceleration mode
Vehicle is not in oil aeration mode
Vehicle is not in low range (if equipped)

Edited March 2, 2019 by tbarn

tbarn · March 2, 2019

Continued

When cylinder deactivation is commanded, the ECM will determine what cylinder is firing and begin deactivation on the next closest deactivated cylinder in firing order sequence. For example, if cylinder number 1 is on its combustion event when cylinder deactivation is commanded ON, the next cylinder in the firing order sequence that can be deactivated is cylinder number 7. If cylinder number 5 is on its combustion event when cylinder deactivation is commanded ON, then the next cylinder in the firing order sequence that can be deactivated is cylinder number 4.

Cylinder deactivation is accomplished by not allowing the intake and exhaust valves to open on the selected cylinders by using special valve lifters. The deactivation lifters contain spring loaded locking pins that connect the internal pin housing of the lifter to the outer housing.

The pin housing contains the lifter plunger and pushrod seat which interfaces with the pushrod. The outer housing contacts the camshaft lobe through a roller. During V8 mode, when all cylinders are active, the locking pins are pushed outward by spring force, locking the pin housing and outer housing together causing the lifter to function as a normal lifter. When cylinder deactivation is commanded ON, the locking pins are pushed inward with engine oil pressure directed from the valve lifter oil manifold assembly solenoids. When the lifter pin housing is unlocked from the outer housing, the pin housing will remain stationary, while the outer housing will move with the profile of the camshaft lobe, which results in the valve remaining closed. One valve lifter oil manifold assembly solenoid controls both the intake and exhaust valves for each deactivating cylinder. There are 2 distinct oil passages going to each cylinder deactivation lifter bore, one for the hydraulic lash-adjusting feature of the lifter, and one for controlling the locking pins used for cylinder deactivation.

Although both intake and exhaust valve lifters are controlled by the same solenoid in the valve lifter oil manifold assembly, the intake and exhaust valves do not become deactivated at the same time. Cylinder deactivation is timed so that the cylinder is on an intake event. During an intake event, the intake cam lobe is pushing the valve lifter upwards to open the intake valve against the force of the valve spring. The force exerted by the valve spring is acting on the side of the lifter locking pins, preventing them from moving until the intake valve has closed. When the intake valve lifter reaches the base circle of the camshaft lobe, the valve spring force is reduced, allowing the locking pins to move, deactivating the intake valve. However, when cylinder deactivation is commanded ON, the exhaust valve for the deactivated cylinder is in the closed position, allowing the locking pins on the valve lifter to move immediately, and deactivate the exhaust valve.

By deactivating the exhaust valve first, this allows the capture of a burnt air/fuel charge, or exhaust gas charge, in the combustion chamber. The capture of exhaust gases in the combustion chamber will contribute to a reduction in oil consumption, noise and vibration levels, and exhaust emissions when operating in V4 mode cylinder deactivation mode.

During the transition from V8 to V4 mode, the Fuel Injectors will be turned OFF on the deactivated cylinders. To help prevent spark plug fouling, the ignition system secondary voltage or spark is still present across the spark plug electrodes on the deactivated cylinders. If all enabling conditions are met and maintained for cylinder deactivation operation, the ECM calibrations will limit cylinder deactivation to a cycle time of 10 minutes in V4 mode, then return to V8 mode for 1 minute.

Edited March 2, 2019 by tbarn

tbarn · March 2, 2019

Continued

Switching between V8 and V4 modes is accomplished in less than 250 milliseconds, making the transitions seamless and transparent to the vehicle operator. The 250 milliseconds includes the time for the ECM to sequence the transitions, the response time for the valve lifter oil manifold assembly solenoids to energize, and the time for the valve lifters to deactivate, all within 2 revolutions of the engine crankshaft.

Valve Lifter Oil Manifold Assembly

The cylinder deactivation system uses an electro-hydraulic actuator device called the valve lifter oil manifold assembly. The valve lifter oil manifold assembly is bolted to the top of the engine valley, below the intake manifold assembly. The valve lifter oil manifold assembly consists of 4 electrically operated normally closed solenoids. Each solenoid controls the application of engine oil pressure to the intake and exhaust valve lifters on the cylinders selected to deactivate. Engine oil pressure is routed to the valve lifter oil manifold assembly from an internal oil passage on the rear of the cylinder block.

All 4 valve lifter oil manifold assembly solenoids are connected in parallel to a fused ignition 1 voltage circuit, supplied by the powertrain relay. The ground or control circuit for each solenoid is connected to a low side driver internal to the engine control module (ECM).

When all enabling conditions are met for cylinder deactivation, the ECM will ground each solenoid control circuit in firing order sequence, allowing current to flow through the solenoid windings. With the coil windings energized, the solenoid valve opens, redirecting engine oil pressure through the valve lifter oil manifold assembly into 8 separate vertical passages in the engine lifter valley. The 8 vertical passages, 2 per cylinder, are connected to the valve lifter bores of the cylinders to be deactivated. When vehicle-operating conditions require a return to V8 mode, the ECM will turn OFF the control circuit for the solenoids, allowing the solenoid valves to close. With the solenoid valves closed, engine oil pressure in the control ports is exhausted through the body of the solenoids into the engine block lifter valley. The housing of the valve lifter oil manifold assembly incorporates several bleeds in the oil passages to purge any air trapped in the valve lifter oil manifold assembly or engine block.

To help control contamination to the hydraulic circuits, a small replaceable oil screen is located in the valve lifter oil manifold assembly oil inlet passage, below the oil pressure sensor. The oil pressure sensor is a 3-wire sensor which provides oil pressure information to the ECM.

During service, use extreme care in keeping the valve lifter oil manifold assembly free of any contamination or foreign material.

Edited March 2, 2019 by tbarn

tbarn · March 2, 2019

Cylinder deactivation may be inhibited for many reasons including the following:

Engine coolant temperature out of range for cylinder activation
Engine vacuum out of range
Brake booster vacuum out of range
Transmission gear incorrect or shift in progress
Accelerator pedal out of range or rate of pedal application to fast
Engine oil pressure and temperature out of range
Engine speed out of range
Vehicle speed out of range
Minimum time in V8 mode not met
Maximum V4 mode time exceeded
Decel fuel cutoff is active
Reduced engine power is active
Torque management is active
Catalytic converter over temperature protection is active
Piston protection is active, knock detected
Cylinder deactivation solenoid driver circuit fau

KARNUT · March 2, 2019

Did you notice close to the end of the video he mentions not just sludge but 'oil delivery' issues? Oil pump. VLOM solenoids, lifter bore tolerance...…. and yes, every once in a while a defect in materials, fit or finish.

Problem with this issue is the number of self inflicted wounds in rational thought. A butterfly in Indochina causes a hurricane in Cuba and the world demands an extinction event for all butterflies.

Had a few flat tires in my life. Should I go back to hard rubber hoops or wooden wheels?

I meant the opposite when I posted this. Back in the day it was thought that an engine would last longer if it was used as a highway cruiser rather than just around town. The thought was less cold start ups and longer up to temperature running. I’ve been convinced that more frequent oil changes are a good idea in most cases, no matter what oil. Why not.? I usually pay more for a dinner night out.

Sent from my iPhone using Tapatalk

pickmeup · March 2, 2019

11 hours ago, Grumpy Bear said:

This just sunk in. Why do we believe over temperature is the only thing that causes 'sludge'? Depleted TBN, water/fuel contamination and short tripping so that the oil never sees a hour in the fully warmed up conditions. Aeration and foaming.

BTW depleted TBN doesn't mean a zero TBN.

Did you notice close to the end of the video he mentions not just sludge but 'oil delivery' issues? Oil pump. VLOM solenoids, lifter bore tolerance...…. and yes, every once in a while a defect in materials, fit or finish.

Problem with this issue is the number of self inflicted wounds in rational thought. A butterfly in Indochina causes a hurricane in Cuba and the world demands an extinction event for all butterflies.

Had a few flat tires in my life. Should I go back to hard rubber hoops or wooden wheels?

Yes it was a good read grumpy . The point he made about seeing pin damage from like pin damage from sequence of events not happening at cam base but under ramp up of lobe. And you can search many other forums and sites and quite a few say same thing ......Going along and all of a sudden stabiltrac light comes on and 15 to 30 seconds later check engine and dreaded misfire felt . Still others report on failure order of lights coming on is reverse order . Just keeps my simple mind stimulated Grumpy

Grumpy Bear · March 2, 2019

2 hours ago, pickmeup said:

Yes it was a good read grumpy . The point he made about seeing pin damage from like pin damage from sequence of events not happening at cam base but under ramp up of lobe. And you can search many other forums and sites and quite a few say same thing ......Going along and all of a sudden stabiltrac light comes on and 15 to 30 seconds later check engine and dreaded misfire felt . Still others report on failure order of lights coming on is reverse order . Just keeps my simple mind stimulated Grumpy

Tell the truth here. This thread is the first I've hear of the Stabiltrac component. Not having access to the wiring and logic diagrams I couldn't hope to form anything but a guess and I hate to guess. Opinions without any foundation...speculation. Sorry, I'm dry well on this one.

diyer2 · March 2, 2019

I have no doubt that some lifter failures are due to mechanical or defect issues.

Some are related to oil issues.

I don't care what the computer says ,the manufacturer says or the oil company's say.

Why risk a problem when oil and filters aren't that expensive.

If your kidneys don't filter your blood, a dirt blanket is coming.

Why not do the same for your motor if you want to keep the vehicle.

Just a thought.

Eddie 70 · March 2, 2019

On 2/9/2019 at 7:21 PM, FL335i said:

Thanks CDNSS. I could at least check the filter under the oil sender. I'm quickly approaching 100k. Might make that the 100k check...

You are a maintenance guy like myself. I am at 108k on mine and since watching the video I am thinking this might be something I just change out at my next oil change. It could be a while since I am not driving my truck daily lately. If you do decide to check yours, I would love to know the results of your findings. I think I'll be ordering a filter and o-ring and having it on hand and swap it.

Austin66 · March 2, 2019

OK....I'm a little confused. Where is the VLOM filter for our DI engines? Those two videos were port injection engines. I had my intake off and don't recall seeing that cylinder shaped thing protruding in the back where the filter resides in. Second, why do I care about the oil sending unit screen and whats that have to do with the VLOM screen?

Edited March 2, 2019 by Austin66

Grumpy Bear · March 3, 2019

2 hours ago, Austin66 said:

OK....I'm a little confused. Where is the VLOM filter for our DI engines? Those two videos were port injection engines. I had my intake off and don't recall seeing that cylinder shaped thing protruding in the back where the filter resides in. Second, why do I care about the oil sending unit screen and whats that have to do with the VLOM screen?

Same screen.