Afm And Oil Consumption

music · January 26, 2011

Please understand that my above comments were just thoughts about what might be happening causing the high oil consumption.

The problem is that most don't do it. If it were predictable, and based on wear, etc., GM themselves would have seen it long before production. There has to be some variable involved... something that makes some do it, while most don't.

Toyota has a "fly in the ointment", so to speak, with the 5.7L ($4k Air Induction Pump). If you read the threads and articles, you'd think the 5.7 was a ticking $$ bomb. Most Tundra owners don't have the problem, but if you do... man-oh-man. The difference, to me, is that Toyota is not taking care of their customers like you'd expect, where GM seems to be trying. At least oil consumption doesn't leave anyone stranded on the side of the road.

chas0218 · January 26, 2011

Update to 2007 Chevrolet Suburban

Service writer called today and said the Cylinder number 1 rod was showing wear. Not sure if tech who replaced pistons and rings forgot to button something up or low oil caused wear over time. They called GM and they are replacing motor. Should get Suburban back tomorrow morning. I asked if all updates had been done to the new motor including the shroud around the oil pan pressure relief valve. They said yes. My concern is what happens in another ~60,000 miles.

Also a note to anyone. Just a thought, when the Active Fuel Management engages, it sends pressurized oil to the lifters that collapse to keep the valves from opening and closing. It looks as if the pressure that builds up as those particular cylinders are compressed would cause air to leak past the rings into the oil pan area pressurizing the oil pan. As the piston is driven back down on the power stroke or intake stroke, the cylinder could become a vacuum sucking air and oil past the rings into the combustion chamber. As wear increases, so does the amount of air/oil leaking past the rings. It looks to me as if you would want to keep the intake valve open on both the power and intake strokes compensating with the computer for the mass air flow rate. Turn off the spark and fuel to the deactivated cylinders when AFM is activated. Then on both compression strokes you would want to allow the exhaust valve to open to allow air to escape the cylinder in order to reduce any drag on the engine. The biggest problem I see is that when AFM is activated with the exhaust valve open during the compression and exhaust stroke it would cause the exhaust to lean out with the added extra air being pumped into the exhaust manifolds which would make closed loop fuel control difficult.

In my opinion, the best thing would be to scrap the ideal. I didn't buy my suburban to get 20 mpg anyway.

mdavidthomas

Matthews, NC

Only issue I have with that is if your PCV valve is working correctly it should not form pressure/vacuum to that extent.

Pyggy · January 26, 2011

Update to 2007 Chevrolet Suburban

Service writer called today and said the Cylinder number 1 rod was showing wear. Not sure if tech who replaced pistons and rings forgot to button something up or low oil caused wear over time. They called GM and they are replacing motor. Should get Suburban back tomorrow morning. I asked if all updates had been done to the new motor including the shroud around the oil pan pressure relief valve. They said yes. My concern is what happens in another ~60,000 miles.

What kind of warranty are they giving you on the new motor? Is there going to be a specific warranty for the motor, or will it just be covered by the existing powertrain warranty?

pm26 · January 26, 2011

Answer from GM on oil consumption:

NORMAL!!!!!!!!

jryan51 · January 26, 2011

2007 GMT900....I took mine in for an "oil consumption test" a month or so ago after it started burning oil around 40k miles....before that it burned 0 per oil change and I change at about 10%-15% on the DIC (6k-7k miles).

The "add oil" came on today so I took it back in as was instructed. I was told 2qts/3k miles was deemed normal...at which point I said, "if you advertised that you'd never sell a truck".

I was expecting that they'd come back with my usage being deemed normal. Surprisingly, they came back with abnormal. Parts are being ordered up to fix.

mdavidthomas · January 27, 2011

Only issue I have with that is if your PCV valve is working correctly it should not form pressure/vacuum to that extent.

I understand that the PCV would work for the crankcase but I don't believe it would affect the pressure inside the cylinder if it is closed by the intake and exhaust valve. One other note, my vehicle had a lifter tick from day one and the car made a vibration sound (growl) when it deactivated the AFM. The new engine that I got back today seems extremely quiet when activating and deactivating the AFM.

Also, I work for a pneumatic cylinder company. If take a brand new air cylinder and plug port on one end of the cylinder it's almost impossible to pull the rod out or push the rod in by hand unless the piston seals allow air to leak from one side of the piston to the other.

mdavidthomas

Matthews, NC

JackedBeaver · January 27, 2011

I'm having no help from the dealer either. Started an oil consumption test, drove 3k miles or so, lost 2q of oil and they are telling me that's normal. It's really such a shame because these are great trucks otherwise. Can't wait untill my warranty is up so I can tune it and get rid of the joke that is AFM altogether.

If anyone on the lot was told that according to GM 2 quarts of oil for every 3k miles is normal, they would never sell another vehicle. I think just knowing that's how ignorant they are makes me want to stay away in the future. Then I remember that all the major brands have their major issues and it's a moot point.

pm26 · January 27, 2011

2007 GMT900....I took mine in for an "oil consumption test" a month or so ago after it started burning oil around 40k miles....before that it burned 0 per oil change and I change at about 10%-15% on the DIC (6k-7k miles).

The "add oil" came on today so I took it back in as was instructed. I was told 2qts/3k miles was deemed normal...at which point I said, "if you advertised that you'd never sell a truck".

I was expecting that they'd come back with my usage being deemed normal. Surprisingly, they came back with abnormal. Parts are being ordered up to fix.

I would think that 1 quart per 3k miles oil consumption would be right at the upper limit of "normalcy" for most vehicles.

pm26 · January 27, 2011

If anyone on the lot was told that according to GM 2 quarts of oil for every 3k miles is normal, they would never sell another vehicle.

About ten years ago Volkswagen played this game with customers when they complained about excessive oil consumption in their VW Beetle 2.0 liter engines. It was in 2 to 3 quarts per 3k miles or more range. It was only after many complaints and threats of lawsuits that VW admitted that there was an issue. It turns out that on many cars the oil control piston rings were installed upside down.

This forced the company to repair many engines under warranty. But of course they at first tried to find an easy way out and do nothing.

ColoradoSkiCountry · January 27, 2011

Well of course, what would you expect from JokesWagon/Audi. They always play games.

If anyone on the lot was told that according to GM 2 quarts of oil for every 3k miles is normal, they would never sell another vehicle.

About ten years ago Volkswagen played this game with customers when they complained about excessive oil consumption in their VW Beetle 2.0 liter engines. It was in 2 to 3 quarts per 3k miles or more range. It was only after many complaints and threats of lawsuits that VW admitted that there was an issue. It turns out that on many cars the oil control piston rings were installed upside down.

This forced the company to repair many engines under warranty. But of course they at first tried to find an easy way out and do nothing.

chas0218 · January 27, 2011

I understand that the PCV would work for the crankcase but I don't believe it would affect the pressure inside the cylinder if it is closed by the intake and exhaust valve. One other note, my vehicle had a lifter tick from day one and the car made a vibration sound (growl) when it deactivated the AFM. The new engine that I got back today seems extremely quiet when activating and deactivating the AFM.

Also, I work for a pneumatic cylinder company. If take a brand new air cylinder and plug port on one end of the cylinder it's almost impossible to pull the rod out or push the rod in by hand unless the piston seals allow air to leak from one side of the piston to the other.

mdavidthomas

Matthews, NC

Sorry I must have mis-read your post. I was thinking you meant within the crank case.

The gas that is trapped in the combustion chamber is supposed to act like a spring and push the piston back down the cylinder during the intake stroke. So in theory it looses no pressure just compresses the spent exhaust gases instead of expelling them on the exhaust stroke.

So in your pneumatic cylinder you would pull the air in then plug both valves keeping the air inside. Which will then compress and expand what air was trapped.

It sounds good in theory but I would think it would cause pre-mature ring wear, which would answer the oil consumption concern.

mtiffinal · January 27, 2011

Stopped by the dealer to check on my truck and was told new lifters are ordered for the drivers side. He also said they would clean the carbon from the rings.

441G · January 27, 2011

Stopped by the dealer to check on my truck and was told new lifters are ordered for the drivers side. He also said they would clean the carbon from the rings.

try to have them change all the deactivation lifters - we had a truck in the shop that had just one stuck closed so we replaced it - a week later another stuck and we were in the motor again!

hillbilly4u · January 30, 2011

(hillbilly4uPosted Yesterday, 11:35 PM)
Went in yesterday for the second 1k consumption check. Has burned 1 qt. in 2 thousand miles. They handed me a paper from GM saying 1 qt. per 3k is acceptable and that I seem to be just a little over that. Don't think they're gonna do much right now unless it gets worse. I bought the truck from a Dodge dealer and the sales rep swore it was not AFM motor. Course thats his word against mine.

Which paper did they give you? The one I have is #01-06-01-011F that states 1qt per 2000 miles. You can look at the RPO codes in the glove box and figure out if it has AFM. There's also a place to enter your VIN and it will tell everything the truck was built with, but I can't remember off hand where that's at.

Yeah, thats the same one. Its a year old. Jan 09. I ran the VIN Decoder from this site for the RPO's. I have the AFM with iron block.

hillbilly4u · January 31, 2011

Guys...the only real fix is pistons and rings.

All the other stuff is a band-aid

Great to see a dealer tech chime in. I'm listening. The question is, do you guys do many, of the few that have these problems? IE change pistons and rings? Or won't GM let you unless consumption is over the little paper they give ya? I see Life is Great with a 4.8 LOL. That should tell some kinda story.

I wouldn't say a thing about the consumption if its not slowly damaging other stuff like cats and 02 sensors. There has to be more techs lurking on this subject. Please let us know what you think?