I bought a 1990 Honda Accord LX in February of this year, since then its been nothing but problems. so just recently i put same year motor in but only difference was i been putting newer parts since march. now my only problem is that the idle revs up then drops and it repeats itself only in Park and in Neutral. any ideas why it does that? i have been reading other post and have done some of the things but nothing has worked.

 

What have you done? IACV, FITA, and TB clean? EGR port and valve clean? Have you bled the air out of the cooling system?

It could be a number of things. Narrow it down for us a bit.

 

I checked the FITV (checked and cleaned), IACV (cleaned and adjusted the yellow snug tight), and there's this thing i checked its on the right side (looking at the motor) of the intake manifold it has a vacuum line to it. bled the cooling system and made sure no air bubbles inside.

 

TB cleaned? what is the EGR port and where is that located

 

Sounds like a vacuum leak. Spray a can of Carb/Brake cleaner around the intake mani, TB, and vacuum hoses to see if the idle drops. Otherwise, your IACV will need to be cleaned. If it's doing just at cold start up, your FITV needs to be adjusted.

 

Interesting.
My 90 accord does this only a handful of times a year and only when cold.

99.9% of the time it doesn't do it.
Is yours behaving this way every cold start?

FWIW, clogged EGR issues usually manifest themselves on these engines by feeling like the engine is missing around 1400-1700 rpms.