I have a 2002 Tahoe with 84,000 miles. Starting around 30,000 miles, a knock could be heard from the engine until it warms up. A friend told me this is common for GM engines, is caused by piston slap, and is nothing to worry about. Has anyone had similar knocking noises?

 

Some of the above vehicles may exhibit an engine knock noise that begins in the first 19,000-24,000km (12,000-15,000mi) of use. The knock noise is most often noticed during initial start-up and typically disappears within the first 5-30seconds (may last longer in extreme cold temperatures). The noise is usually more noticeable on the initial start-up when the temperature is below 10°C (50°F) and may be more pronounced on the first cold start following a long trip.
This noise may be caused by an interaction between carbon that has formed on the piston, the piston motion and the cylinder wall. GM Powertrain Engineering, and an analysis of engines with this condition, has confirmed that the noise is not detrimental to the performance, reliability or durability of the engine. THIS NOISE DOES NOT HAVE ANY EFFECT ON THE LONGEVITY OF ANY OF THE ENGINE COMPONENTS.
Important:At this time, attempts to repair this condition by replacing the engine assembly or pistons are not recommended.
Please share the information found in this bulletin with customers who inquire about this condition. In the event they have additional questions or concerns, please advise your Area Service Manager.