I have a question about an engine knock/ticking noise that I have comming from the engine of my 02 GMC Sierra (5.3L). This knocking sound only happens at startup when the vehicle has been sitting for a while such as over night. The sound only last for about 2 minutes and then goes away and does not come back unless the vehicle sits for longer than 5 to 6 hours between driving it. Also the knocking noise seems to be more noticible and has a longer duration in when it is colder outside. I have only owned this vehicle for a year and it only has 100k miles on it and I planning on having this vehicle for a long time. I wanted to find out if this noise is common for this motor or if this could be the sign of a more serious issue. Could it be from the oil not pumping up into the engine fast enough? I have been using the recommended 5W-30 grade for this motor. Any helpful insight into what may be causing this issue would be appreciated.