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Afm Turned Off..problem Solved..


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#1 GMC Yukon XL

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Posted 19 March 2010 - 05:42 PM

Well I've been keeping close eye on my oil level after buying a programmer to turn off the AFM several weeks ago...

I really dont want to start a war so I will explain the problem that I was having..

I do alot of driving...My truck has alittle over 160k on it.. Its a 2007 GMC Sierra SLT nbs 5.3.. I Love my truck.. I"m hoping to get 200k on it before I trade.. but for as long as i can remember it was using oil...about a quart every 4k.. I started using mobil 1 I think after or around 20k miles.. I always change my oil every 5k-6k miles.. I dont care what anyone says 5k-6k is perfectly fine if your using synthetic..

Anyway back to my oil consumption issue..It never got worse..My add oil light would come on it after every 4k.. but recently I noticed after coasting down a long long hill at least 1\2 a mile with my foot completely off the gas the whole time & when you stepped back on the pedal the exhaust would blow out blue smoke....If you coasted a mile or more it would leave a 40-50 foot long trail of blue smoke when you stepped back on the gas...then it would clear up after the oil burned out of the cylinders that were turned off while coasting....

You could start the truck up @ -20 & rev it up..No smoke...It would NEVER smoke any other time..

Went on a road trip awhile back & our freinds that were following us called & said what on earth is wrong with your truck!!?!

Otherwise I never would have noticed....Dealership said it was normal to use oil..I said is it normal for it to Smoke???? Kinda ticked them off by saying that but I never got anywhere..

Was told by my mechanic it could be a leaking valve guide seal..Well when I first start the truck in the morning it should puff out some blue smoke..That usually means valve guide seals... But it wasnt doing that..

I wondered if somehow with it in 4cyl mode if it was pulling oil up past the rings or maybe pulling it in else somewhere else..

Bought a Programmer & turned off my AFM..over 2500 miles so far now & oil hasnt budged on the dipstick..Right at the full mark... & no smoke after coasting 1\2 a mile or more..

I may never know exactly why it was pulling oil into those cylinders but what I do know is my truck isnt using anymore oil... :thumbs:

Edited by GMC Yukon XL, 19 March 2010 - 05:46 PM.


#2 redvett

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Posted 19 March 2010 - 06:00 PM

1 qt to 4000 miles is really good oil usage and you will very doubtful get more than that even with AFM turned off. You tested your truck for 160K and GM has for millions of miles in varied conditions. You had to pay for the programmer and that cost wont make up for the oil used. Upper cylinder lubrication is needed or increased wear will result. If you drove 40K and changed oil at 5000 mi your only talking 8 changes, saving at best 1/2 qt oil in 5K will be pressing it. Face it ALL piston engines have to and always will use oil.

#3 M. Cueva

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Posted 19 March 2010 - 06:00 PM

Well I've been keeping close eye on my oil level after buying a programmer to turn off the AFM several weeks ago...

I really dont want to start a war so I will explain the problem that I was having..

I do alot of driving...My truck has alittle over 160k on it.. Its a 2007 GMC Sierra SLT nbs 5.3.. I Love my truck.. I"m hoping to get 200k on it before I trade.. but for as long as i can remember it was using oil...about a quart every 4k.. I started using mobil 1 I think after or around 20k miles.. I always change my oil every 5k-6k miles.. I dont care what anyone says 5k-6k is perfectly fine if your using synthetic..

Anyway back to my oil consumption issue..It never got worse..My add oil light would come on it after every 4k.. but recently I noticed after coasting down a long long hill at least 1\2 a mile with my foot completely off the gas the whole time & when you stepped back on the pedal the exhaust would blow out blue smoke....If you coasted a mile or more it would leave a 40-50 foot long trail of blue smoke when you stepped back on the gas...then it would clear up after the oil burned out of the cylinders that were turned off while coasting....

You could start the truck up @ -20 & rev it up..No smoke...It would NEVER smoke any other time..

Went on a road trip awhile back & our freinds that were following us called & said what on earth is wrong with your truck!!?!

Otherwise I never would have noticed....Dealership said it was normal to use oil..I said is it normal for it to Smoke???? Kinda ticked them off by saying that but I never got anywhere..

Was told by my mechanic it could be a leaking valve guide seal..Well when I first start the truck in the morning it should puff out some blue smoke..That usually means valve guide seals... But it wasnt doing that..

I wondered if somehow with it in 4cyl mode if it was pulling oil up past the rings or maybe pulling it in else somewhere else..

Bought a Programmer & turned off my AFM..over 2500 miles so far now & oil hasnt budged on the dipstick..Right at the full mark... & no smoke after coasting 1\2 a mile or more..

I may never know exactly why it was pulling oil into those cylinders but what I do know is my truck isnt using anymore oil... :thumbs:



Good to hear that you took care of the smoke issue. I bet that the AFM engaged was pulling a little too much oil...IMO

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#4 Super Stealth

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Posted 19 March 2010 - 07:09 PM

This is an excellent observation.

GM has many TSB's out for "over-active" lifters on AFM equipped engines.

OK. So, the AFM lifter body physically changes during AFM operation and under "released (normal)" operation. We all understand that.

BUT, can the amount of oil going THRU the lifter (during afm) have any effect on ACTUAL OIL CONSUMPTION.

That is the OP's topic here guys.

For his truck to consecutively burn oil, 160k miles documented, then he turns OFF Afm. Now his oil level is normal and full.

Don't the rest of you see what I see??

Could the AFM lifters, when in their engaged (afm) state, continuously pour too much oil up in the cylinder heads??

TSB...."over-active" lifters...................

TSB... a great influx of oil-burning engines...since 2007......
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#5 michigan2500hd

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Posted 19 March 2010 - 09:22 PM

This is an excellent observation.

GM has many TSB's out for "over-active" lifters on AFM equipped engines.

OK. So, the AFM lifter body physically changes during AFM operation and under "released (normal)" operation. We all understand that.

BUT, can the amount of oil going THRU the lifter (during afm) have any effect on ACTUAL OIL CONSUMPTION.

That is the OP's topic here guys.

For his truck to consecutively burn oil, 160k miles documented, then he turns OFF Afm. Now his oil level is normal and full.

Don't the rest of you see what I see??

Could the AFM lifters, when in their engaged (afm) state, continuously pour too much oil up in the cylinder heads??

TSB...."over-active" lifters...................

TSB... a great influx of oil-burning engines...since 2007......

Very interesting....lets keep this thread going...who knows ...we may find an answer here.
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#6 M. Cueva

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Posted 19 March 2010 - 09:25 PM

I vote to use his truck as a test truck.
Turn On AFM for exactly 1000 miles and then check oil level, document results
Change Oil
Turn Off AFM for exactly 1000 miles and then check oil level, document results
repeat 10x

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#7 Daryl Z71

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Posted 19 March 2010 - 10:08 PM

1 qt to 4000 miles is really good oil usage and you will very doubtful get more than that even with AFM turned off. You tested your truck for 160K and GM has for millions of miles in varied conditions. You had to pay for the programmer and that cost wont make up for the oil used. Upper cylinder lubrication is needed or increased wear will result. If you drove 40K and changed oil at 5000 mi your only talking 8 changes, saving at best 1/2 qt oil in 5K will be pressing it. Face it ALL piston engines have to and always will use oil.




My 05 never used any oil for the 36,000 miles I owned it, and my 09 hasn't used any in the 12,000 miles Ive had it so far. Glad to hear your problem cleared up. I wonder if this is why mine threw blue and black smoke the other night when my buddy was behind me, and I stepped on the gas. Oh well mine will be turned off next month anyhow.

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#8 weagle99

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Posted 19 March 2010 - 10:27 PM

What programmer did you use to turn AFM off? Did you buy an extra ECM also?

#9 Sir Dan

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Posted 19 March 2010 - 11:40 PM

You're avatar says 2001 Yukon XL, is there an update? :flag:
What year and model are we talking about here?

Edit: Sorry, just read a little closer: "2007 GMC Sierra SLT"
Seems like it may be a bad omen of things to come with your AFM lifters, even tho the oil burning has stopped for now ...Maybe you should have let the dealer put some replacement "bad" lifters back in for ya?? :lol:

I read somewhere that as the cylinders are disabled with AFM, the oil leaks into them and as they are re-activated the oil that leaked into them is burned, hence the smoke. Only thing is, these lifters leak all the time, regardless of AFM being on or off, you just don't see the smoke cause the oil is being burnt off all the time. Although this doesn't explain why your oil comsumption issue stopped with AFM disabled.... The Mystery goes on...
Did you use Diablosport?

Edited by Sir Dan, 20 March 2010 - 12:05 AM.

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#10 Riverjet502

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Posted 20 March 2010 - 07:08 AM

Just wait till the tree huggers read this post..They will be wanting to put filters in your exhaust like the diesel boys and choke your exhaust up so you get poorer milage....lol.lol..
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#11 Ryan00TJ

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Posted 20 March 2010 - 07:15 AM

You're avatar says 2001 Yukon XL, is there an update? :flag:
What year and model are we talking about here?

Edit: Sorry, just read a little closer: "2007 GMC Sierra SLT"
Seems like it may be a bad omen of things to come with your AFM lifters, even tho the oil burning has stopped for now ...Maybe you should have let the dealer put some replacement "bad" lifters back in for ya?? :lol:

I read somewhere that as the cylinders are disabled with AFM, the oil leaks into them and as they are re-activated the oil that leaked into them is burned, hence the smoke. Only thing is, these lifters leak all the time, regardless of AFM being on or off, you just don't see the smoke cause the oil is being burnt off all the time. Although this doesn't explain why your oil comsumption issue stopped with AFM disabled.... The Mystery goes on...
Did you use Diablosport?


I would still like to know how oil is leaking into the cylinder or combustion chamber? Oil coming from the lifter thru the pushrod to the rocker arm is pooled in the head and drains back thru the drain holes in the head/block. It cannot get in here unless a valve stem seal or valve guide is leaking. When AFM is working I don't believe there is anything different in how those cylinders receive oil vs when in V8 mode.
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#12 NickV

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Posted 20 March 2010 - 08:11 AM

This is an excellent observation.

GM has many TSB's out for "over-active" lifters on AFM equipped engines.

OK. So, the AFM lifter body physically changes during AFM operation and under "released (normal)" operation. We all understand that.

BUT, can the amount of oil going THRU the lifter (during afm) have any effect on ACTUAL OIL CONSUMPTION.

That is the OP's topic here guys.

For his truck to consecutively burn oil, 160k miles documented, then he turns OFF Afm. Now his oil level is normal and full.

Don't the rest of you see what I see??

Could the AFM lifters, when in their engaged (afm) state, continuously pour too much oil up in the cylinder heads??

TSB...."over-active" lifters...................

TSB... a great influx of oil-burning engines...since 2007......


all LS1 based motors (which includes the 4.8L, 5.3L and 6.0L) have been known to consume approximately 1 qt of oil in about 5,000 miles. I observed this in my 2003 4.8L truck at EVERY oil change. I measured how much oil was removed and I always filled to 6 qts., I never had more than 5 qts. and I changed my oil every 5,000 miles with Mobil 1 full synthetic 10w30.

WARNING: Above advice is based on actual experience or just plain common sense. In the event said advise is determined to be incorrect you are entitled to a full refund of exactly what you paid for it.

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#13 NickV

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Posted 20 March 2010 - 08:15 AM

You're avatar says 2001 Yukon XL, is there an update? :flag:
What year and model are we talking about here?

Edit: Sorry, just read a little closer: "2007 GMC Sierra SLT"
Seems like it may be a bad omen of things to come with your AFM lifters, even tho the oil burning has stopped for now ...Maybe you should have let the dealer put some replacement "bad" lifters back in for ya?? :lol:

I read somewhere that as the cylinders are disabled with AFM, the oil leaks into them and as they are re-activated the oil that leaked into them is burned, hence the smoke. Only thing is, these lifters leak all the time, regardless of AFM being on or off, you just don't see the smoke cause the oil is being burnt off all the time. Although this doesn't explain why your oil comsumption issue stopped with AFM disabled.... The Mystery goes on...
Did you use Diablosport?


I would still like to know how oil is leaking into the cylinder or combustion chamber? Oil coming from the lifter thru the pushrod to the rocker arm is pooled in the head and drains back thru the drain holes in the head/block. It cannot get in here unless a valve stem seal or valve guide is leaking. When AFM is working I don't believe there is anything different in how those cylinders receive oil vs when in V8 mode.


my best guess would be that it's the vacuum created sucking in oil. during "V4" mode the lifters compress, therefore not pushing the push rods, which don't push the rocker arms, which don't open the valves. In that state, the piston is still cycling up and down, however the valves are closed, when the piston drops it creates a vacuum, best I can figure it's creating a suction and bringing in some oil around the rings.

either way, the 4.8, 5.3 and 6.0 have been known for oil consumption since 1999, long before AFM.

WARNING: Above advice is based on actual experience or just plain common sense. In the event said advise is determined to be incorrect you are entitled to a full refund of exactly what you paid for it.

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#14 GMC Yukon XL

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Posted 20 March 2010 - 10:26 AM

What programmer did you use to turn AFM off? Did you buy an extra ECM also?


I almost had Blackbear turn it off but I deicided a handheld programmer would be better for the money...When I trade in for a new truck "Avalanche" I should be able to return the stock tune on mine & use it on my next truck..If not I'll sell it to a buddy..

I bought the Diablo Predator..I installed the performance tune for about 10 minutes & I really didnt notice anything different in power..Maybe alittle..I reinstalled the factory tune & turned off the AFM & turned off the speed limiter..I didnt buy it to increase my power I bought it with the intentions of turning off the AFM.. If I want more power next time around I"ll buy something with a bigger motor..

NickV that is exactly what I thought the problem was..It only takes a drop of oil in 1 cylinder to create smoke..

I've heard the horror stories about the lifters in these trucks but lifters arent my problem.. I've seen another post on this board of somebody with a white sierra or silverado parked in a garage with blue smoke everywhere & so I read it had something to do with his afm lifters being bad..

My Sierra has never done that...The Engine runs as smooth as it did when it was new.. No Rattling or stuck lifters.. etc
My Yukon would Piston slap something horrible after starting it cold..This 5.3 doesnt...


In 160k+ miles of burning a quart every 4k & recently noticing the blue smoke upon coasting 1\2 a mile or longer & then turning off the afm & after 2500+ miles my oil level hasnt dropped at all.. Everytime I've checked it has been with the motor cold & its been right on the F mark...By now it would have been @ the halfway mark on my dipstick..& its not.. I can coast a mile or longer & I no longer have the blue smoke pouring out of it when I step on the gas pedal...

I'll check again @ 5k before it gets changed & repost again..But like I said before..@ 2500 miles it was always down halfway on the dipstick..& now its not...

#15 CalixEros

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Posted 20 March 2010 - 06:27 PM

You're avatar says 2001 Yukon XL, is there an update? :flag:
What year and model are we talking about here?

Edit: Sorry, just read a little closer: "2007 GMC Sierra SLT"
Seems like it may be a bad omen of things to come with your AFM lifters, even tho the oil burning has stopped for now ...Maybe you should have let the dealer put some replacement "bad" lifters back in for ya?? :lol:

I read somewhere that as the cylinders are disabled with AFM, the oil leaks into them and as they are re-activated the oil that leaked into them is burned, hence the smoke. Only thing is, these lifters leak all the time, regardless of AFM being on or off, you just don't see the smoke cause the oil is being burnt off all the time. Although this doesn't explain why your oil comsumption issue stopped with AFM disabled.... The Mystery goes on...
Did you use Diablosport?


I would still like to know how oil is leaking into the cylinder or combustion chamber? Oil coming from the lifter thru the pushrod to the rocker arm is pooled in the head and drains back thru the drain holes in the head/block. It cannot get in here unless a valve stem seal or valve guide is leaking. When AFM is working I don't believe there is anything different in how those cylinders receive oil vs when in V8 mode.


my best guess would be that it's the vacuum created sucking in oil. during "V4" mode the lifters compress, therefore not pushing the push rods, which don't push the rocker arms, which don't open the valves. In that state, the piston is still cycling up and down, however the valves are closed, when the piston drops it creates a vacuum, best I can figure it's creating a suction and bringing in some oil around the rings.

either way, the 4.8, 5.3 and 6.0 have been known for oil consumption since 1999, long before AFM.


The cylinders are full of air when the valves close so there's not a vacuum when the piston's on the downstroke. If they didn't, you wouldn't gain effeciency with AFM. If the valves were left open, as they used to be on early versions of this type of system, pumping losses would minimize efficiency gains.

A GM engineer explained to me that localized cooling of the shut off pistons in V4 mode allow a little more oil to sneak past the piston rings and get burned off when the cylinder kicks back on. This is one of the reasons the AFM is only allowed to be on for so long before it forces V8 mode back on regardless of throttle position. I can't verify this to be true; it's just what I've been told.




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