Here are the car specs...
89 civic 1.5, dual point fuel injection , auto trans.

problem...
idles at around 1250 rpm even when fully warmed up ( in park ) place it in gear and idle drops to 1000 rpm idle isn't fluctuating just too high. the check engine light is not on ( it does work ) and no codes flash from the ecu

what I have done so far...
cleaned throttle body , checked vacuum hoses , sprayed around throttle body , intake manifold and any other areas looking for vacuum leaks , replaced iacv , topped off and bleed cooling system , changed oil( needed it)
side note.. after oil change the idle while in park dropped to 1000 from 1250 but only stayed there for a few minutes then back up to 1250. don't think this car has a fitv valve ( sp? ) so... with all this in mind any other things to check? hate to tap out and take it to a shop so any help will be greatly appreciated.
Thank you from a newbie.

 

have you changed the pcv?
does it idle down when you put pressure on the throttle to close?

 

My 90 did that every so often until I ran a few tanks of Lucas injector cleaner through it.

 

Have not changed the pcv , throttle plate appears to be shut all the way at idle speed. the throttle cable has deflection. question... is there a learning process that the ecu has to go through after replacing the iacv to return to normal idle( providing the iacv was the only problem ) have yet to drive the car since doing this work only let it idle.

 

I run the lucas injector cleaner every 6000 miles ( just added a bottle with this oil change )

 

Pinch off the hose that goes from the side of the air box to the IACV to make sure the IACV is closing fully. When idling above specified rpm, the IACV should be closed fully and no air flowing through that hose. Also disconnecting the wires to the IACV should make no difference.

I think on the DPFIs it is legit to adjust the throttle plate stop screw to set up idle but before touching anything there, obtain and read the service manual.

 

Pinched off that hose....engine speed dropped/stumbled. removed and replaced that hose as it appeared to have a couple of crackes in it near the bottom where it attaches to the intake manifold. ran the car with this hose loose from the air box... lots of vacuum pull at the hose with the too fast idle. reattached this vacuum hose. unplugged wire harness to the iacv with car running... idle dropped super low( almost stalled ) reattached wires and cleared the code that was set. perhaps there is still a vacuum leak somewhere... have looked at all the lines over and over.. have sprayed around all lines and throttlebody and everywhere else I could think of with t/b cleaner and wd40 listening for change in engine speed didn't notice any. someone suggested using a small propane tank and using the unlit propane to find a vacuum leak. I don't know. think it's time to tap out and take it to a shop

 

Having it slow down when you disconnect the IACV wire means that the ECU is in command of the idle speed like it should be. It may be too fast because the ECU is getting an incorrect reading from the ECT (coolant temperature) sensor. While the ECU thinks that the engine is cold, it will make it idle fast.

Or the idle is normal, and your tach reads fast. Don't trust dash tachs to set up idle speed.

 

Checked the ECT and bingo... it was bad. changed it and happy days car idles just fine. strange.... read the haynes manuel over and over till my eyes bled. don't remember any mention of this sensor being a possible culprit. much thanks to ya for all the helpful tech info... greatly appreaciated.