Naming and memorizing vehicles is not something just children with autism do.
I have seen typical children take interest in things and memorize each one as well. However often in typical children you will see their interests change and not stay the same. I would worry when my son would be intrested in something, but his intrests have always changed and he would even hae a few at one time. Another example being a friends of ours son knew every single Thomas the Train but had now moved on to knowing every Dinasour. He is 3 and believe me he is very typical in every other way. I would even say he is advanced. I know because my son was not typical, so I can compare.
As far as temper. All children handle their anger differently typical or non typical. I have heard of kids that grind their teeth, stomp their feet, kids will hit etc. Again this is not just something that austisitc kids do.
If you are not having luck with pediatricians that be should be a good sign NOT to rely on typical pediatricians. If your truly concerned you need to find a Developmental Specialist or Devlopmental Psychologist in your area. you may even need to get more than one opinion. Depending where you live you may find a Universitiy you can go to.
Look up symptoms of Aspergers on the internet mabey and do a checklist for now. Of course the internet CAN have some bad info. so take it with a grain of salt. Good luck
Pulling out hair is a major symptom of an anxiety disorder called "trichotillomania". Frustration and temper tantrums are also behaviours of children suffering from anxiety. A search of the internet might give you more idea concerning this anxiety disorder.
jas make sure you as a parent spend lots of time with your child, try to be interested in what he is interested in, you could also give him some multivitamins just to ensure he is properly brain and body develop, try visiting this site http://www.besthealthoptions.com, it has plenty of articles about child and baby care. i've learned a lot from it. gud day!
Another suggestion is to look for a DAN (Destroy Autism Now) doctor in your area. You can look up on the internet.
Do your children or your 3yr old go to daycare? Is there anyone that you know of that is around them or him on a regular basis w/out you around?
The reason I am asking... his behavior "could" have something to do w/ being abused; either mentally or sexually.
I say this because I was mentally and sexually abused when I was a child. No one knew it, I didn't tell anyone. I lashed out by being physically abuse to my parents, friends and teachers. I would bite, hit, scream... I was very ugly to people because I didn't trust anyone. The abuse lasted till I was 12 so it took me along time to get over it. If I would have told someone when I was little - it would have stopped and I could have gotten help alot earlier and been a much happier child.
IF this is not the case and you know for-sure he's not being abused, then it could be he is trying to get affection and attention from you. He might feel left out w/ his other brothers around.
I can say that I know how that feels too - I have kids of my own now, a great husband... and I will never, never put them through what I went through. I give them so much love and attention. I know "we" always say there is not enough time in the day... but there is... for your family. Take time to sit, talk, read, play with not only all of them at the same time, but also individually! It will make a hugh difference if you do that (that's if you're not doing that already)!
Best of luck to you... I feel for him.