The idle-dipping disease.
I’ve done the searching and am hoping you guys (especially if you’ve fixed yours!) can help!
Usually when coming to a quick clutch-brake stop. Drops to 500 RPM, shakes car a little, sometimes stays for a few seconds, then returns to normal 750 RPM. On a odd occasion will do the dip a few seconds later also. Car always drives like a champ, no missing, stumbling or anything during driving. Car will NEVER do the dip during warmup cycle, ONLY does it once warmed up, and it only dips randomly, not always. Has never stalled the car yet.
I also get a decent dip to 500-600 RPM’s when using power windows and/or rear defroster button. Car usually idles fine within factory spec otherwise.
Recently double-checked alternator charging (good) and replaced battery with little or no change. Recently replaced coolant temperature sensor. All grounds look clean & solid. Everything on intake looks clean & tight, I have a cone filter & MAF adaptor w/ disconnected AIV hose as my intake setup. I’m thinking a possible TPS issue. What should I be doing first here? Maybe a vac leak? Seems unlikely but who knows.
Any other ideas? Problem seems to be very slowly getting worse, and I want to get to the bottom of it before my car starts stalling out at lights. :?
Thanks! 
Idle Air Control Valve… its either not work proper and could just need a good cleaning… or the seal is shot and its leaking so isnt getting a proper reading… ?
I honestly don’t know where the IAC valve is, can someone post an engine bay pic or explain…you might be onto something.
Thanks. Keep it coming.
http://www.zeroyon.com/TheSite/techservice.html
you can download a manual there and check it out
its on the intake manifold
Yeah i’m an idiot I should’ve thought of that…
Found some good stuff in there, thanks.
When the car idles normally on the car, it is 750 RPM right on.
So, I will look into TPS, grounds, IAC valve.
That said, keep the suggestions coming y’all! 
hey im having the same trouble with my car…
its a 1990 SOHC…
but im trying to look for the idle air control valve(IACV), in the PDF’s…
but cant find ne info on it at all…
can someone plez tell me where its located?
thanx
Chaz
It will not be the TPS causing the problem… if that was gone then when you step on the gas the car would act funny… either not wanting to move or it would move then stop then move then stop kinda thing… because its never getting the right reading from the pedal etc…
it is for sure the idle air control
I’m pretty sure not 100% but its in the middle of the intake manifold or what not… so it comes from the head and does a half circle… well its on the inside of the circle sorta? so I’m guessing as well you need to remove the whole manifold in order to replace it/clean it…
I’ll go take a picture thou and double check
Sorry it is extremely dark but you should be able to get the idea as to where its located now
thanx a bunch,…
cuz i would prob have no clue as to where it was i was cleaning!!
lol…
thanx again!
Chaz
I should have mentioned one other thing in my original post…
0-3 times a day driving: if I let off the gas quick the car seems to let off, then go back on again a few times by itself, all within 1-2 seconds after releasing gas. Causes a couple brief “jerks” type of thing. Typically around 3000-4000 RPM. Other times it seems to control fine when I let off accelerator quickly.
Has never been a big problem or anything…but that’s why I wanted to look into TPS, just in case, as well.
Anyone else fix this type of problem BTW?
Thanks again all…
I tightened my throttle cable. That seems to have just about entirely fixed it!
If anyone reads this w/ similar problems, try that first, make sure your throttle cable is tight.
IACV is on the end of the manifold close to the firewall at the bottem. It’s a flat screw driver to adjust it.
okay i attempted to remove and clean the IACV…
but i cant get at the bolts…
can someone tell me what kind of tool they used to remove these bolts…
i really need to clean the IACV, the idle is really bugging me now,
because i know what the problem is but cant get at the bloody bolts…
ne ways hope someone has information on this!
ne info will help…
Thanx
Chaz
Update: Throttle cable fix was temporary…my idle-dropping is still very present!
Negative battery (and other) grounds all seem fine.
So, I finally tried the advice of Sven as best as I could while taking pictures to help everyone…please help me track down what is okay, and what is BAD. This way hopefully we can get this cleaned up into a FAQ/How-To so everyone with idle issues can try this stuff first. But i’ll need your help, so here goes:
First I cleaned/checked the harnesses:
2 teeth were missing, don’t know if this is normal or not, but that was my first strange observation of this whole thing…
Then, these 3 connectors, which I believe Sven & jjm were talking about in an earlier post:
#1 - was cleaned ok.
#2 - not sure what it was, how to remove this? I was tempted to pry the whole unit off the metal peg or pull the sleeve back…or is there a clip somewhere etc??? Didn’t want to break this…and it was really dirty, could be an issue!
#3 - Not sure what this was either, how is it unclipped? Again, did not want to break…
Please see if you can help me out guys, thanks!
Those plugs will not be your problem. Our cars are OBD I it only coolent temp sensor for cold start most of the time, the other is your sensor for you temp gauge and the last is the knock sensor. Did you ever touch the thottle cables??? If you did adjust em or some thing happend with them that is your problem. There may not be enough slack in the cable.
The throttle cable was too loose, my mechanic double-checked and agreed, tightening it.
This fixed the problem for a day or so, then it seems as though “the ECU adjusted” to the new tightness or something, and the dip is back.
I’ll admit, the dip isn’t terrible or anything, the car drives like a pro. It doesn’t go below 500 RPM. I just don’t want it to start stalling, like in other posts i’ve read! And, I want to get to the bottom of it.
I’m gonna reground everything on my car with new quality wiring. I’m gonna see if that fixes things up and then i’ll take things from there.
Thanks smurf6x6!
I would still recheck the throttle cables. The thottle plate can be open ever so slightly and it will cause it. I done it before on my own car and was getting fustrated checking everything else cause i thought the cable were fine. When one of the techs told me to check the thottle cables.
So would more tight or more loose be a better thing?
Because when I tightened it, it felt like a new car, great! Instant throttle response. Idled high for a few seconds then came down okay. Should I tighten more or less? Where would the cruise cable come into this as well? I’ve had them both tightened.
I’m thinking I will tighten them both a bit more and see how things feel…sound good?
Thanks BTW.
There is some sorta of Throttle Plate cleaner as well by 3M i think?
I used it once on a Mazda Protege and my weird-idle went away "was just to much built up dirt on the plate i suppose causing problems in how it sealed or opened or shut ? no sure… but it was like a $7 quick fix
If your Idle dips thou… 200rpm “around” then its not the throttle cable
I screwed with many many things until cleaning the Idle control valve and replaced the seal then my troubles were over with!
just to bad the KA manifold isnt like a B series honda one… they IACV is just on the back side of the manifold and is sooo easy to get at and remove
