not so sure about that, but I think it has something to do with vtec. cause if i have my car in neutral, and I am not rolling, the engine will not engage in vtec. So, since your speed sensor aint working, the computer may not engage vtec. I am not sure tho, but from my experiences, vtec don't kick in unless im rolling. I know cause I hooked up a vtec light to run everytime vtec kicked in. Hope that helps.