Civic EG

I recently rebuilt my d15b7 for daily drive
I am not sure if I am missing something here, I turned on after put motor in my lx and somehow it had difficult times to start up, felt like rumbles then I tried again and it started up and went up to 2k rpm and I left it on for like 4-5 min finally it went down to 800 rpm.. i turned it off and tried again in few hours. It started to act like that again. Is it bad spark plug? Spark plug wire? Bad starter ground?

Thanks
Dj

If it jumps to 2k, you have a vacuum leak somewhere.

If its my vacuum leaking caused rpm to bouncing like that, do I have to replace the whole hose?

What hose would you be talking about? I'd pull your intake tube off and start your car and cover the throttle body. The car should die almost instantly. If it doesn't, re-connect the tube and use carb cleaner to spray around until you find the leak

I wasn't sure what about the hose because I was researched it on the other site
All right I will try it with carb cleaner

Also when you said to spray around with a carb cleaner, where do I have to spray it at?

I researched about idle issues and believe it must be dirty amd filthy FTIV. I will get it cleaned when it is not rainy day.

FIXED!
It was FTIV
Cleaned it with brake cleaner and installed it back. Runs perfect