Heads up on Active Fuel Management by GM.

[Bubba1235]

Just heard about this and still don't know what to say. A buddy has a newish Chevy (09 or 10 I think) that has the 5.3 L. V-8 with active fuel management. That's GM speak for shutting down some cylinders when the power isn't needed.

Ok, so he just topped 100K miles and started noticing he was down a quart or so with the last oil change so he's stayed on top of it. It's gotten a LOT worse in the last couple months and is really using oil. Took it to the local dealer and the mechanic did a quick compression check saying he almost knew what the cause was before he did it. He was right, some cylinders had really low compression, the rings are shot. Long and short, it's a known problem with ALL the engines with active fuel management.

From what professionals are saying (after having torn a lot of engines down) the cylinders that get "shut down" are the ones going bad. It seems that the problem is that when you shut them down the cylinder (piston and rings contract) cools down quickly but the block which has coolant running through it really doesn't, or at minimum not as fast and you end up with rings and pistons that are sloppy loose and they wear out way too fast. The mechanic that worked on my buddies truck said this is the third or forth one he has seen personally.

Of course GM isn't doing much of anything about it, at least so far other than re-flashing the computer and disabling the active fuel management system. Don't see how that helps if the damage is already done though...

Cross this engine off the list if you are shopping for a vehicle, especially a used one.

 

[WIMUSKY]

Re: Heads up on Active Fuel Management by GM.

RAM has the same system in their Hemi, 1/2 tons only. Haven't heard about similar issues. Not saying it isn't happening, just haven't heard about it....

 

[roscoe]

Re: Heads up on Active Fuel Management by GM.

I think this is the same problem that has been around for a couple years.
Or, its a separate issue that causes oil consumption.

I know the local dealer has had a bunch of the 5.3 that were using oil.
I also know that if you press the issue hard enough, they have some solutions, and in at least one case (my uncle) they tore down the engine and fixed it under warranty.

 

[dingbat]

Re: Heads up on Active Fuel Management by GM.

I'm scratching my head on this. The cold cylinder would indeed create excessive ring clearance but I don't understand how increasing the the clearance would induce ring wear? You would have blow by and oil use from the the excessive clearance, but ring wear to the point they need replaced?

 

[bruceb58]

Re: Heads up on Active Fuel Management by GM.

Well, if you google it, the claim is that there are extra deposits on the rings due to the colder cylinder.

 

[agallant80]

Re: Heads up on Active Fuel Management by GM.

This is a well known issue with the "new" design starting in 07. GM ended up rebuilding my engine for me under this issue. Though it has nothing to do with your friends theory. The issue was corrected but apparently there were some in stock that made it in to later model trucks.

My truck has the infamous 5.3L oil consumption problem.

 

[Fleetwin]

Re: Heads up on Active Fuel Management by GM.

I don't doubt it. You are basically turning several cylinders into an air compressor.

The pressures created, when a cylinder fires, help keep the compression rings seated against the cylinder wall. When the cylinder isn't firing, that does not happen to the same extent. Not different than a cylinder misfire, left not addressed, will cause cylinder damage-eventually.

I also think there is some validity to the theory that several cylinders running cool, in the same block, may cause some cylinder issues.

To my knowledge, only Fiat (Chrysler) and GM are doing this.

Some may remember the Cadillac 8/6/4 engines of the early 1980's. They didn't have this issue because they never ran that long. They failed due to inferior electronic controls that just were not sophisticated enough to make the transitions seamless.

 

[dingbat]

Re: Heads up on Active Fuel Management by GM.

#10-06-01-008A: Engine Oil Consumption on Aluminum Block Engines with Active Fuel Management (AFM) ( Install AFM Oil Deflector and Clean Carbon from Cylinder) - (Sep 28, 2010)


Subject: Engine Oil Consumption on Aluminum Block Engines with Active Fuel Management (AFM) (Install AFM Oil Deflector and Clean Carbon from Cylinder)


Models: 2007-2008 Cadillac Escalade, Escalade ESV, Escalade EXT

2007-2008 Chevrolet Avalanche, Silverado 1500 , Suburban, Tahoe

2007-2008 GMC Sierra 1500, Sierra Denali, Yukon, Yukon XL, Yukon Denali, Yukon Denali XL

2008 Pontiac G8 GT

Equipped with Aluminum Block V8 Engine with Active Fuel Management (AFM) (RPOs LC9, LH6, L76, LFA, L92)

with Greater than 45,000 km (28,000 mi)




--------------------------------------------------------------------------------

This bulletin is being revised to update the Condition/Cause/Correction sections, add 4WD labor time and add information about replacement of spark plugs if necessary. Please discard Corporate Bulletin Number 10-06-01-008 (Section 06 - Engine/Propulsion System).


--------------------------------------------------------------------------------

Condition
Some customers may comment about engine oil consumption of vehicles with higher mileage (approximately 48,000 to 64,000 km (30,000 to 40,000 mi). Verify that the induction system is assembled correctly and that there is no evidence that the engine has been ingesting dirty air due to a mis-assembled induction system. Also verify that the PCV system is functioning properly. If diagnostic procedures indicate that oil consumption is piston/piston ring related, verify that oil consumption is less than 3,000 km (2,000 mi) per liter/quart. If these conditions are met and oil consumption is less than 3,000 km (2,000 mi) per liter/quart, perform the service indicated in this bulletin.

Cause
This condition may be caused by oil spray that is discharged from the AFM pressure relief valve within the crankcase. Under most driving conditions and drive cycles, the discharged oil does not cause a problem. Under certain drive cycles (extended high engine speed operation), in combination with parts at the high end of their tolerance specification, the oil spray quantity may be more than usual, resulting in excessive deposit formation in the piston ring grooves, causing increased oil consumption.

Correction
To correct this condition, perform the piston cleaning procedure as described in this document, and install a shield over the AFM pressure relief valve per the procedure outlined in this document. Monitor oil consumption after this repair to ensure oil consumption has improved to acceptable levels. If this repair does not correct the condition, it may be necessary to replace the piston assemblies (piston and rings) with new parts.

Important: It is critical in this cleaning process that the engine/fuel injector cleaner remain in the cylinders for a minimum of 2.5 hours to fully clean the components. The cleaner solution must be removed before a maximum of three hours.

Verify the oil consumption concern following Corporate Bulletin Number 01-06-01-011F. If oil consumption is found, continue on with this bulletin.
Remove the spark plugs and ensure that none of the pistons are at top dead center (TDC).
Clean the pistons by putting 118-147 ml (4-5 oz) of Upper Engine and Fuel Injector Cleaner, GM P/N 88861802 (in Canada, use 88861804), in each cylinder. Allow the material to soak for at least 2.5-3.0 hours, but no more than three hours and then remove the cleaner. A suggested method of removing the cleaner is cranking engine over. Make sure to unplug the ignition coils and fuel injector before cranking the engine over. Also make sure that the painted surfaces are covered so no damage is done.
Remove the oil pan. Refer to Oil Pan Replacement in SI.



Remove the AFM valve (1).



Install the new shield (1), GM P/N 12639759, and tighten the AFM valve to the oil pan to 28 N?m (20 lb ft).
Important: Ensure that the engine cleaner is thoroughly removed before reinstalling the spark plugs. Failure to do so may result in a hydro-lock condition.

Reinstall the spark plugs. Replace the spark plugs if necessary due to full of carbon. Refer to the parts catalog.
Reinstall the oil pan. Refer to the Oil Pan Installation procedure in SI. Replace the oil pan gasket if necessary. Refer to the parts catalog. Replace the engine oil if necessary.
Re-evaluate the oil consumption. Document on the repair order. If the oil consumption is still greater than 0.946 L (1 qt) in 3,200 km (2000 mi), replacement of the pistons and rings will be required.
Parts Information
Part Number
Description
Qty

12639759
DEFLECTOR-OIL PRESS RLF VLV (quantity of 3 per order)
1

88861802 (in Canada, use 88861804)
CLEANER, F/INJR 16 OZ LIQUID POUR (Upper Engine and Fuel Injector Cleaner)

 

[greenbush future]

Re: Heads up on Active Fuel Management by GM.

My 5.3 doesn't burn oil, however there are more issues with the 2008 year, basically my entire top end of my engine required rebuilding. all the lobes on my cam were worn off, due to this same reduced cylinder technology. Had it not been under warranty I would have had to eat these cost's, mine did this at 45K and runs great now that it's been fixed. If you check the bulletins on these motors you will see ALL the issues they had, and there were a few.

 

[Fleetwin]

Re: Heads up on Active Fuel Management by GM.

I think GM realized what was going on and devised a solution-hat's off. Basically, it boils down to those cylinders not contributing. In other words-heat. They were over oiling those cylinders that were not contributing to power. Understood.

Let's see what Fiat/Chrysler/Dodge does.

 

[GA_Boater]

Re: Heads up on Active Fuel Management by GM.

I think GM realized what was going on and devised a solution-hat's off. Basically, it boils down to those cylinders not contributing. In other words-heat. They were over oiling those cylinders that were not contributing to power. Understood.

Let's see what Fiat/Chrysler/Dodge does.

Maybe Tony did it right the first time, unlike GM adding the shield to reduce oiling the "cold" cylinders as an afterthought. With this problem showing up at 30-40K miles, it sounds like engine testing results were ignored or overlooked. Who knows?

 

[avenger79]

Re: Heads up on Active Fuel Management by GM.

just a quick thought because he made it to 100K without issue and now noticed an issue, did he change his PCV recently? it should be changed regularly and if it's not you will notice oil consumption much greater than expected.