Intermittent starting problem

[Hethj7]

Some may remember this problem from the summer. Sometimes when starting my car, the starter stays engaged. There are even times when I can turn the key back off and the starter still runs. I am pretty sure the solenoid was welding itself closed.

I thought I had finally determined that it was a bad ground, so the system was looking for ground back through the starter, causing it to run and the solenoid to get hot and weld itself closed.

I have worked with it a few times and am almost certian that losing a ground is not the problem. I have replaced the solenoid, started, alternator, and the ignition switch in the steering column and am still having this problem.

Since I am at school now, I don't have access to tools, garage, etc. I took it to a shop and of course they started it up about 50 times and it never did it. I drove it a few more days with no more problems, then yesterday it did it twice. What do I do?

I don't have a way to do much work on it here at school, and it is intermittent and may not happen if I take it to a shop. Any suggestions?