IMPORTANT: The Chronicles of Low Oil Pressure by 07burb

[Andrew1068]

With the fresh oil and filter those oil pressure numbers are within spec. I would monitor the situation over the next few weeks going forward.

Replacing the O-ring on a 4x4 truck is more involved due to the front axles but everything else remains the same.

Yea my plans are weekly monitoring or bi weekly depending then stretch it slowly if everything stays the same. The dip stick is burnt black so I believe the shop that was changing the oil hasn' really been changing the oil.

 

[CobraKing]

The AFM (Cylinder De-Activation) can lead to oil consumption issues. You should monitor oil levels on a monthly basis.

 

[Andrew1068]

The AFM (Cylinder De-Activation) can lead to oil consumption issues. You should monitor oil levels on a monthly basis.

I was actually reading an oil consumption thread earlier and they suggested a catch can and eliminating the AFM through a tune. The afm is what controls the switch from 8 to 4 cylinders when driving under steady speeds?

 

[HiHoeSilver]

I was actually reading an oil consumption thread earlier and they suggested a catch can and eliminating the AFM through a tune. The afm is what controls the switch from 8 to 4 cylinders when driving under steady speeds?

Yes, and it's killing your motor behind your back. You can do a few things....
1. Disable it with a Range device that plugs into the OBD port.
2. Disable it with a tune.
3. Drive it in M5? (I think.... Someone with first hand knowledge, please advise)
4. Go the whole 9 yards, and mechanically eliminate the AFM. I believe @iamdub can describe this.

 

[iamdub]

Yes, deleting the AFM (Active Fuel Management) by mechanically removing the crappy parts is best. Second best is to disable it. Disabling just keeps it from engaging so it stays in 8-cylinder mode. As was said, this can be done with a plug-in Range device or, better yet, a tune. The tune is better than the Range because you can have many other things tweaked. Disabling MAY be a permanent solution for you but I'd bank more on it just buying time. The failure-prone AFM lifters are still in the motor. Mechanically deleting it involves opening up the motor and removing these lifters as well as a few other AFM-specific parts and replacing them with non-AFM parts, either OEM or aftermarket. If you ever considered getting an aftermarket cam, this is a perfect time to do this. The PCM will still need to be tuned to at least turn off the AFM in the programming. A few performance companies offer AFM delete kits that have all the hard parts you'll need in one package. I've never priced them out, but they may or may not be cheaper than sourcing all the parts yourself. I like Texas Speed's approach- you can start with the base kit that includes just 8 lifters to replace the AFM lifters only or build it up from there with 16 new lifters (my choice) to no cam or a stock cam or one of their performance cams, etc.

 

[Andrew1068]

Yes, deleting the AFM (Active Fuel Management) by mechanically removing the crappy parts is best. Second best is to disable it. Disabling just keeps it from engaging so it stays in 8-cylinder mode. As was said, this can be done with a plug-in Range device or, better yet, a tune. The tune is better than the Range because you can have many other things tweaked. Disabling MAY be a permanent solution for you but I'd bank more on it just buying time. The failure-prone AFM lifters are still in the motor. Mechanically deleting it involves opening up the motor and removing these lifters as well as a few other AFM-specific parts and replacing them with non-AFM parts, either OEM or aftermarket. If you ever considered getting an aftermarket cam, this is a perfect time to do this. The PCM will still need to be tuned to at least turn off the AFM in the programming. A few performance companies offer AFM delete kits that have all the hard parts you'll need in one package. I've never priced them out, but they may or may not be cheaper than sourcing all the parts yourself. I like Texas Speed's approach- you can start with the base kit that includes just 8 lifters to replace the AFM lifters only or build it up from there with 16 new lifters (my choice) to no cam or a stock cam or one of their performance cams, etc.

Alright thanks so much. I've got a message out to my performance shop to find out about a tune as well as cost to install. I found the Texas speed kit which I'll be buying.

 

[JonnyTahoe]

No, top of the block at the back near the fire wall where the pressure sensor is at. You take the pressure sensor out then that pulls out. Another reason why it's EXTREMELY important to do regular oil changes. Not 100% about how often the previous owner changed the oil prior to us owning it.

 

[techbiker]

Yes, and it's killing your motor behind your back. You can do a few things....
1. Disable it with a Range device that plugs into the OBD port.
2. Disable it with a tune.
3. Drive it in M5? (I think.... Someone with first hand knowledge, please advise)
4. Go the whole 9 yards, and mechanically eliminate the AFM. I believe @iamdub can describe this.

Has anyone identified exactly how the AFM system damages lifters, the cam, and eventually the bottom end? I'd like to keep AFM unless it's shown to be faulty. Perhaps the AFM problems can be minimized through preventative maintenance?:

-Replace leaking/dripping fuel injectors to keep gasoline out of the oil
-Perform more frequent oil changes while using a synthetic oil- and perhaps a higher weight?
-Use an oil drain plug with a magnet
-Replace AFM lifters with new ones every 100k? Lifters are apparently cheap and easy to change on these motors.
-Do not use FRAM oil filters
-Prime new oil filters with oil during each change

My hunch is that one's risk of an AFM lifter failure increases with deferred maintenance.

 

[iamdub]

Has anyone identified exactly how the AFM system damages lifters, the cam, and eventually the bottom end? I'd like to keep AFM unless it's shown to be faulty. Perhaps the AFM problems can be minimized through preventative maintenance?:

-Replace leaking/dripping fuel injectors to keep gasoline out of the oil
-Perform more frequent oil changes while using a synthetic oil- and perhaps a higher weight?
-Use an oil drain plug with a magnet
-Replace AFM lifters with new ones every 100k? Lifters are apparently cheap and easy to change on these motors.
-Do not use FRAM oil filters
-Prime new oil filters with oil during each change

My hunch is that one's risk of an AFM lifter failure increases with deferred maintenance.

The AFM system doesn't damage lifters. The special lifters for the AFM system are more failure-prone than regular lifters, mainly due to their extra moving parts and smaller oil passages. The cam gets damaged by a failed lifter, either by it collapsing and getting beat around or fragmenting and sometimes rotating in the bore.

Yes, about the only prevention one can do is proper maintenance. But, no amount of PM or top-quality oil will improve the "weak" design of the AFM lifters so failure will always be a possibility.

Keeping clean oil of the correct viscosity is critical. The lifters have smaller passages than regular lifters so they're more susceptible to being clogged by gunk in the oil. Since they are hydraulic lifters, oil weight and viscosity is an important factor and the manufacturer-recommended oil should be used.

A magnetic oil plug or, better yet, a FilterMag would be good to help hold metal particles should something fail or begin to wear excessively. But, it won't really/directly prolong the life of the AFM components.

You could replace the lifters every 100K miles or whatever interval you choose. But, with the cost (money, time, hassle, etc.) of doing this procedure, you're continually band-aiding a problem when you're literally millimeters from removing the problem. Besides, this likely won't happen more than twice (assuming you're starting with a sub-100K mile motor) because I doubt there are any AFM motors making it to 300K like the Gen3 motor commonly do.

Do the math: Unless the extreme majority of your driving is cruising around 60MPH or below with no adverse traffic on flat and smooth roads with no headwind for miles and miles at a time, the 1-2 MPG improvement that AFM may return is far negated by the risk and expense of keeping it "alive". Yes, you can run the priciest synthetic oils and change them excessively frequently as extra-cautious preventative maintenance. But don't forget you'll be needing to add extra quarts of your fine synthetic oil between OCIs due to the AFM system causing more oil consumption. Which, by the way, causes extra carbon buildup in the combustion chambers and on the pistons and can lead to more extensive damage.

So, spend a few hundred extra on parts and a weekend of labor every 100K miles, a couple hundred extra in oil over the life of your motor, randomly/possibly unnecessarily cleaning or replacing fuel injectors, continually having the risk of the system failing and taking out your motor (which you know will only happen while you're out on the open road with your family on a road trip), etc... all to save MAYBE a couple hundred bucks in fuel over a 200K mile lifespan? You're stepping over a dollar to pick up a dime.

 

[techbiker]

The AFM system doesn't damage lifters. The special lifters for the AFM system are more failure-prone than regular lifters, mainly due to their extra moving parts and smaller oil passages. The cam gets damaged by a failed lifter, either by it collapsing and getting beat around or fragmenting and sometimes rotating in the bore.

Yes, about the only prevention one can do is proper maintenance. But, no amount of PM or top-quality oil will improve the "weak" design of the AFM lifters so failure will always be a possibility.

Keeping clean oil of the correct viscosity is critical. The lifters have smaller passages than regular lifters so they're more susceptible to being clogged by gunk in the oil. Since they are hydraulic lifters, oil weight and viscosity is an important factor and the manufacturer-recommended oil should be used.

A magnetic oil plug or, better yet, a FilterMag would be good to help hold metal particles should something fail or begin to wear excessively. But, it won't really/directly prolong the life of the AFM components.

You could replace the lifters every 100K miles or whatever interval you choose. But, with the cost (money, time, hassle, etc.) of doing this procedure, you're continually band-aiding a problem when you're literally millimeters from removing the problem. Besides, this likely won't happen more than twice (assuming you're starting with a sub-100K mile motor) because I doubt there are any AFM motors making it to 300K like the Gen3 motor commonly do.

Do the math: Unless the extreme majority of your driving is cruising around 60MPH or below with no adverse traffic on flat and smooth roads with no headwind for miles and miles at a time, the 1-2 MPG improvement that AFM may return is far negated by the risk and expense of keeping it "alive". Yes, you can run the priciest synthetic oils and change them excessively frequently as extra-cautious preventative maintenance. But don't forget you'll be needing to add extra quarts of your fine synthetic oil between OCIs due to the AFM system causing more oil consumption. Which, by the way, causes extra carbon buildup in the combustion chambers and on the pistons and can lead to more extensive damage.

So, spend a few hundred extra on parts and a weekend of labor every 100K miles, a couple hundred extra in oil over the life of your motor, randomly/possibly unnecessarily cleaning or replacing fuel injectors, continually having the risk of the system failing and taking out your motor (which you know will only happen while you're out on the open road with your family on a road trip), etc... all to save MAYBE a couple hundred bucks in fuel over a 200K mile lifespan? You're stepping over a dollar to pick up a dime.

Thank you for the info!

The funny thing is that I spend the most time cruising on perfectly flat roads with relatively little traffic and not much wind for miles at under 60 mph. Basically, North Texas in a nutshell unless I get on the freeway or get stuck in traffic during rush hour. I drive at least 12 flat miles at about 50 mph each day to visit our properties. Some days I drive 100+ miles, probably averaging out at 60 mph (can be boring as hell). Even still, I agree that losing AFM probably won't make a huge mpg impact. Downtime for repairs isn't a killer since our Tahoe is mostly a work vehicle and we have other vehicles.

I did not see a noticeable oil loss over 220 miles of driving. I performed deletes on my 300zx due to concerns about the systems failing prematurely. Now I am wondering if my Z would be worth more in a "stock" condition. Would you pay more for a Tahoe without AFM lifters?

Thanks again