My car is having an idling problem where it will idle back and forth between about 2000 rpm down to about 500 rpm and then it will eventually stall. This just started happening after completing my 5 speed swap and after having the intake off. What could it be, an intake leak, timing, the P/N switch?

 

A vacuum leak would be more consistent then that. My guess is one of your sensors is not operating correctly. IAC maybe? You might have a leak in one of the components that are activated by vacuum but only at specific times. EGR or something. The EGR should not have vacuum going to it at idle though.

 

Well the idling problem went away and now it is stalling right after I start it up. It will always start, but it dies right after it fires up.