Rough idle for a 1990 legacy

[1990LegacyLSss]

My 1990 legacy didnt idle for about a week so i replaced the MAFS, cleaned the throttle body, cleaned the air intake valve, replaced the PCV valve, replaced the PCV hose to the air intake. After all that she finally idles but its really rough it bounces from 0- about 1000 rpm is there any reason it is still idling rough? fuel filter? im not sure please help me out 

[Bushwick]

How old are the vacuum lines?

 

Vacuum lines might "look" OK but if original it's a sure bet some have failed given the age. They can harden and split (you won't find the split unless you manipulate every section of hose). They can also soften up and rot in a small section or conversely dry rot. Harder to trace air leaks can occur at the actual nipple where the hose will stretch and harden like that over the years. While it looks like it's attached, in reality it's loosely sitting there. Other areas to inspect are any plastic " T " or " I " junctions, as well as any plastic nipples on sensors. They can get very brittle and snap easily while doing something else and it'll go unnoticed until engine runs rough.

 

For $10, you can replace every piece of vacuum line. Can get it by the foot at parts store and easily do it in their parking lot. I noticed my 95' idled a little more consistently after replacing mine. Biggest thing on mine were several had hardened at the nipples and were loose. ANY tight lines on plastic nipples, I strongly suggest scoring the rubber with a razor to break the seal and the hose will just fall off. When reattaching, use a drop of WD-40 or even spit works. Otherwise you run a risk of a brittle nipple breaking while to slip a new vacuum line over it.

 

You also might have an intake manifold leak somewhere or even your throttle body could leaking. Can try spraying around the flanges (engine cold to reduce flash fires) and see if the engine surges or not. Respraying the suspected leaky area should result in consistent surges.