Excessive Oil Consumption

snocross418 · August 9, 2010

#PIP4574M: Excessive Oil Consumption And/Or Blue Exhaust Smoke - Investigation Update - (Aug 5, 2010)

Subject:Excessive Oil Consumption And/Or Blue Exhaust Smoke - Investigation Update

Models:2007 Buick Rainier

2007-2008 Chevrolet Avalanche, Silverado, Suburban, Tahoe, Trail Blazer

2007-2008 GMC Envoy, Sierra, Yukon

2008 Pontiac G8

2007-2008 Saab 97x

with a 5.3L or 6.0L Aluminum Block V8 Engine

and AFM (Active Fuel Management)

RPOs LC9, LH6, L76, or LFA

This PI was superseded to include revise the affected RPO codes, specify that this is for Aluminum Block Engines only, update models and provide a general update on the status of this investigation in step 5. Please discard PIP4574M.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:

Some customers may complain that their vehicle has been using approximately 1 quart of oil every 500-1,000 miles. In most cases, the customer will advise that this did not start until the engine accumulated approximately 30,000 miles or more. In some cases, the customer may note that this is more apparent when driving at highway speed. In rare instances, a SES light and engine misfire may be encountered with a P0300 DTC.

Upon inspection, an oil fouled spark plug(s) may be noted. In most cases, static compression and cylinder leakage testing will appear normal. Excessive oil may or may not be found in the intake manifold.

In most cases, this is the result of stuck oil control rings. Generally, the stuck oil control rings are the result of excessive oil on the cylinder walls. The excessive oil can come from the PCV system and/or the AFM pressure relief valve in the oil pan.

Recommendation/Instructions:

If this concern is encountered, follow the steps below:

<LI type=1>Visually inspect the entire engine and the underside of the vehicle for any evidence of oil leaks and repair them as necessary. <LI type=1>Inspect the fresh air hose/pipe that is attached to the RF (passenger side) valve cover and all related connections for restrictions, such as plastic casting flash or a pinched hose, and repair as necessary. A restriction in this area may cause excessive crankcase vacuum and oil consumption through the PCV vacuum tube. <LI type=1>If the truck has an engine misfire and a spark plug that is obviously oil fouled, skip to step 4 since this proves that it has an obvious oil consumption concern. If not, perform an oil consumption test as outlined in the latest version of oil consumption of 01-06-01-011 to verify the concern before proceeding to step 4. Allow the vehicle to sit on a level surface with the engine off for at least 10 minutes to allow the entire engine to drain back to the oil pan before checking the engine oil level and adding oil. Compare the oil consumption test results to one of the scenarios below to determine further direction:

• If oil consumption is Less than 1 quart of oil every 2,000 miles and no low oil light has been experienced, no repairs should be performed as this should be considered acceptable oil consumption as outlined in the latest version of 01-06-01-011.

• If oil consumption is Less than 1 quart of oil every 2,000 miles but the customer has experienced a low oil light, refer to the latest version of PIP3959 for a potential low oil light sensor concern.

• If the dealership verifies that oil consumption is More than 1 quart every 2,000 miles, perform the steps below as necessary:

<LI type=1>Determine if the engine has been ingesting oil through the PCV system by removing the intake manifold and measuring how much oil can be poured out of the throttle body opening with the throttle body removed. It is normal to get a couple of teaspoons of oil out of the intake. If the engine has been ingesting oil through the PCV system, several ounces of oil will be measured, many times as much as a 1/4-1/2 quart.

• If the engine HAS NOT been ingesting oil through the PCV system, go to step 5.

• If the engine HAS been ingesting oil through the PCV system, inspect the PCV baffle as outlined in the rest of Step 4 below:

4a. Remove the LH (driver's side) valve cover and inspect the PCV baffle drain holes shown below to see if they are plugged with hardened oil deposits. If they are plugged, replace the valve cover, ensure that the customer is changing their oil according to the maintenance schedule in their owner's manual, and re-evaluate the concern. Generally, this would not be a concern until several thousand miles have accumulated.

4b. With the LH (driver's side) valve cover removed, inspect the PCV baffle to ensure that it is properly sealed to the valve cover by flipping it over and adding a little oil to the corner of the valve cover as shown below. The oil should stay in place as shown on the 2 outer valve covers below. If the oil drains into the PCV baffle as pointed out on the middle valve cover below, replace the valve cover. Generally, if this is the cause of the concern, it would have been present early in the life of the vehicle or shortly after valve cover replacement.

Important: If Step 4a or 4b led to valve cover replacement, perform Step 4b again on the replacement valve cover before installing it.

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• 4c. If the engine HAS been ingesting oil through the PCV system but the valve cover passed the tests outlined above, the engine may have an over-aggressive lifter that is causing the oil ingestion through the PCV system. Sometimes the lifter may be doing this intermittently so it is not always possible to isolate one by inspecting the lifter flow with the driver's valve cover removed. As a result, it is suggested to replace all 8 of the left/driver bank lifters due to the oil in the intake and re-evaluate the oil consumption concern. The right/passenger side lifters should not cause oil in the intake so there is no need to replace them. If the vehicle returns with excessive oil consumption but is no longer ingesting oil through the PCV system, it most likely has stuck oil control rings as outlined in Step 5.

If the engine HAS NOT been ingesting oil through the PCV system and there are no obvious valve seal concerns, this is most likely the result of the AFM pressure relief valve in the oil pan spraying oil on the bottom of the cylinders when active fuel management is on. This may eventually cause the oil control rings to stick and increase the rate of oil consumption. As outlined in the July 2010 GM STC Service Know-How Emerging Issues Seminar (10210.07D), a related bulletin is going to be released to repair this by cleaning the oil control rings and installing a shield over the AFM pressure relief valve. This bulletin was scheduled for a July 2010 release but the bulletin is still going through the final stages of the release process. At this time, it is on track for a mid-August release date. Once released, you will be able to find the new bulletin in the New Bulletins Section of Service Information and this PI will be updated to include the bulletin number as well.

If you would like to view the July 2010 GM STC Service Know-How Emerging Issues Seminar (10210.07D) mentioned above, you can find it by following this path:

• Go to the GM Training Website. (If necessary, there is a link to this website at GM Global Connect "Dealerworld")

• Enter your Training Person ID and Password.

• Click the "Service Know-How/TECHAssist" Link

• Click the "Emerging Issues" Link

• Click the "Searchable Streaming Video" Link

• Click the "10210.07D - July 2010 Emerging Issues" Link

• Click the 9th Link down for High Oil Consumption

Notice: Piston and Ring sets should no longer be replaced for this concern unless it is absolutely necessary. If stuck oil control rings are found and you decide to replace all 8 pistons and all 8 piston ring sets, we DO NOT recommend honing or deglazing the cylinder walls due to the great variation between equipment, machine shops, and technicians performing these repairs. This is because it is generally unnecessary and can induce unnecessary cylinder wall and/or piston ring damage if it is done incorrectly or not cleaned thoroughly. The cylinder walls just need to be cleaned thoroughly with brake cleaner before the new piston and ring sets are installed. At this time, you may also experience a back order situation if you order new pistons and rings.