Looking for ideas on Rough Idle Fix
 

i dont drive a honda.. but as far as I know the prob Im having is experienced on many early 90s japanese 4cyl engines

the symptoms are : a vibration felt through the chassis when the engine rpm is in the spec range (750ish).. it goes away when in park or neutral, but this is most likely because the rpms shoot up to 900-1000. it also goes away when u add some throttle in gear.

ive changed a couple of engine mounts, and done a tune-up.. ran some Injector cleaner, de-carbed the intake and combustion chamber and now im looking for any insight cuz Im sure hondas have experienced this same problem

some things im thinking about is : vacuum leak, idle valve, uneven cylinder compression, or the tranny.

i am going to be selling the car, it runs fine and has no codes but it brings down the value and makes for an annoying ride in stop and go.. u can always jack up the idle so its at 900 and 1250 in park but that cant be too good in the long run.

interested to see what u guys think...

When you say you've done a tune up, what does that involve??? Because plugs may not be the problem. Are experiencing back firing, hesitation??? Try doing a compression test for all cylinders...could be loss of compression. Check the oil and it's color...see if there's contaminated coolant and oil. Check all the wires for continuity too. Loss of compresssion can be due to a blown headgasket or burnt piston rings. One of the wires could be arching too and you could be running on only 3 cylinders...there could be soooooo many possibilities. Do those for now and tell me what you've discovered.

Hope that helps for now.

Cheers,
Buddah.

coolant and oil is fine and dandy..

wires are niehoff and they dont all click in all the way.. they do when i put them on on the plug outside of the well but they just wont fit on inside the well. shoudlve gotten ngk wires to go with those plugs but i dont think thats the problem.

vacuum reading showed a bad intake valve.. sprayed CCC in through the intake vacuum to decarb intake and engine.. cars runs better now and has more power but its still idles rough and when its cold.. (first couple mins) i get a stumble/miss when i accelerate in park..

i have the same problem
 

i have the same problem what is ccc?

combustion chamber cleaner

check antifreeze level, check for coolant leak, bleed cooling system, remove idle air control valve and clean with throttle cleaner, clean throttle plate. Check all hoses and connections.

Hope this helps.

the idle valve is gonna be a beotch.. but i can do it.. have to take off the whole throttle body for access.. might as well clean that out really well and change the gasket there. its only like 4"
i definetely wont replace the idle valve but ill clean it out using TBC and an air compressor. i heard that does the trick a lot of time.
thing is my idle doesnt lope.. my car just has the shakes when it falls down to about 750rpm as theres a certain load there..
could it still be a mount?? only one that hasnt been changed is tranny mount under battery tray, but from the looks of it it doesnt look like its worn..

coolant done.. well refilled.. not bled.. theres no codes at all and the car has passing emissions so its a real challenge trying to find the culprit.

many have said its common at cars with a mileage of 250,000km and its not worth finding it.
id like to prove them wrong, but also not spend much on it.