Not your typical rough idle?

[thecrow7841]

OK, First of all thank you for taking your time to read about my problem.

CAR: '91 LX
Problem: rough idle. car would drop down to 500 or lower RPMs.

When I got the car running(about two months ago,more or less) I had to
replace the exhaust manifold, due to it being cracked before the o2 sensor.
so I replaced the exhaust manifold with an no name one( a gift from a friend late Christmas present) that he got from ebay, and relocated the o2 to the downpipe.

I also Did a tune up, wires,spark plugs, cap and rotor, and PCV. changed the
IAT. somewhat cleaned egr ports. cleaned IAC checked the FITV and tightened the white screw in there. Adjusted the Idle screw and reset the ecu. I messed with the timing and after all that my little problem still continues

One last thing, I DID check CELs but no codes.

Once again, your help is appreciated.

[cloudasc]

Have you checked for vacuum leaks?

[thecrow7841]

Have you checked for vacuum leaks?

ah I knew i forgot to mention something.
Yes i also check for vacuum leaks.
Thanks

[JDM_CB7_TX]

Possibly an injector issue???

[bigbadnothing85]

a reaaaaaaaaaaaaally plugged up tb? IM gasket leak?

[Flatline]

does it do it all the time or sometimes?
My H will sometimes idle down to there for a second or two but come back up.
I would also just put my lights on, then shut them off and its fine.

[Losiracer2]

does it do it all the time or sometimes?
My H will sometimes idle down to there for a second or two but come back up.
I would also just put my lights on, then shut them off and its fine.

wierd, my H22 also does that when I turn on/off the foglights and the headlights. When I drive for a bit, then shift into park, it does that bouncy idle thing but only when either the headlights or foglights are on. And I made sure I grounded each foglight to the fender.

[eazyduzit509]

I spent a few weeks driving with the rough, erratic idle. So, after i spent $50 on a complete intake manifold (injectors and all) i thought, hmmm. So, for some reason i decided to play with my idle screw. As i turned it in to lower the idle it went from the 1000rpm-2500 rpm to a smooth 800rpm... Ive never heard anyone else that adjusted their iddle and fixed the problem but thats exactly what i did, and even to this day once in a month or two it does it again. So i stop, pop the hood and turn the idle down (rattles open) and its good.

[ibr_adam09]

does it do it all the time or sometimes?
My H will sometimes idle down to there for a second or two but come back up.
I would also just put my lights on, then shut them off and its fine.

same here with the idle drop, but it would do so randomly at stop lights for a sec

[bigbadnothing85]

now this isn't from 4-banger experience here.... seems like you guys have severe voltage drop issues... mine kinda does it... every time i turn on my signal i watch my tach drop a bar every time the light blinks lmao... ground straps and generators... gotta love em ... but could this cause the issues? i experience ya'll symptoms, but only with all the lights and wipers on...