I have an 02 f-250 5.4 gas . When I leave my house in the am I never let it warm up. Turn the kay and drive away. I drive about 1 mile and get on the hwy. 1-1/2 miles down thw hwy there is a small hill. Truck with blow blue smoke out the exhaust everyday for about 15 seconds going up this hill. Then will clear and not do it again till the next morning. Any ideas , shouild I be concerned?