3.6L LY7 Rough Idle - keywords carbon contamination fouled fuel oil plug spark sparkplug V6

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

New vehicles that are driven only on dealer parking lots or customer vehicles that are only driven on short trip cycles may exhibit rough engine idle, especially during engine warm-up. This may be caused by fuel contamination of the engine oil and/or carbon fouling of one or more spark plugs.

To correct this condition, check the fuel adapts using the Tech 2. If fuel adapts are off more than 5%, change engine oil and oil filter and reset the fuel adapts. If the engine idle is still rough after changing the oil and resetting fuel adapts, or if the fuel adapts were OK to begin with, remove all six spark plugs and check for carbon fouling. Replace any spark plugs that are carbon fouled with the higher heat range spark plugs listed in the parts catalog.

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.