Blue Oil Smoke From Exhaust At Operating Temperature - Inspect Valve Guide - keywords consumption cylinder deposit engine foul fouled fouling head hot idle intake light plug SES smoke spark

This PI was superseded to revise the recommendation/instructions text. Please discard PIP4165A.

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

Important: This PI does not apply to other models with the same engine. It only applies to the models above if the last 8 digits of the VIN are 77374720 - 77378216.

On rare occasions, blue oil smoke from the exhaust may be noted at operating temperature at idle, or on acceleration after an extended idle/deceleration. This may be the result of oil entering the intake port and combustion chamber of cylinder 2 by bypassing the outside diameter of either intake valve guide.

If this concern is encountered, turn the engine off as the concern is occurring and remove the spark plugs for inspection. If the #2 spark plug has oil deposits on it but the other 3 spark plugs look normal, remove the intake manifold and inspect the bottom 1/4" of both #2 intake valve guides for a vertical groove that may have been mistakenly machined into the outside diameter of either valve guide. Typically, the groove will be facing the intake port opening. If there is no groove present but it is obvious that there is excessive oil in either of the #2 intake ports when compared with other intake ports, remove the related valve spring and valve seal to inspect the other end of the valve guide for this groove. If a machined groove is found on either end of the valve guide, replace the cylinder head using the part number listed in the GMSPO catalog and evaluate the concern.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.