My wife's van is blowing the vacuum hose off the top of the manifold when she starts it up after it sits for a few minutes after running. You can hear it pop and then it idles real fast. Every so often it blows the hose going to the brake booster off also leaving a hard brake pedal and no brakes. Anyone have any idea what would cause it to blow off those hoses?

 

I have an idea but first, how does it run when it is not blowing the hoses off?

 

It runs fine. It only blows them when she starts it back up, after driving a while. It don't do it all the time just on occasion.

 

It has to be back firing into the intake manifold to do that. Something else is wrong. If it seems to run good, might be cross firing under start up conditions. (damp wires, cap if it has one, etc.)