I have a neighbor that has a very loud truck and he feels that it needs revved up with he starts it to go to work at 4:00 in the morning. I was wondering if there was a sound ordinance or some kind of vehicle ordinance that I could report him for.

Probably depends on what city you live in.  I am more annoyed with the morons who drive by with their music blaring.  I doubt that they have any clue that they are bothering others.  Have you said something to the neighbor?  It might be a problem which he is unable to fix without help.  He might not realize that he is bothering people.

The city also has a page that lists contacts for a variety of problems (at http://www.loganutah.org/site/id/complaintresourcetable.htm).  It suggests calling the police for noise in the night (10 P.M. to 7 A.M.).  The number is given on the page.  Good luck (hopefully you resolved this a long time ago, but this may help with your new neighbors...).