I have a 1992 civic SI with the 1.6l and I just chanced the motor with one from the junk yard because my old head was bad, So heres the problem, When I first start it up it idles at like 1500rmp but it keeps jumping up and down a couple of hundred RPMs until it is warm, the light is on and it says iacm but I have tryed 3 and no better(not to mention it didnt do it befor the swap) I cant find any vacumme leaks I checked the Idle valve under the throttle body and the white ring was lose so I tightened it up and no better, I think it is shot because when it is hot I cover that port behind the butterfly and there is still a ton of suction, if I cover both of them holes it drops to 500rpms and if i cover the whole tb it dies ,I have turned the screw up just a hair to open the buterfly so it would idle and not stall at every corner but if i turn on the ac it still stalls. besides i dont think that is the answer to the problem just a quick fix. I tested the iacm buy putting power to it and it clicked so it should be good but dont know for sure. I check the voltage in the tps and it was .33 at closed and 4.48 open so i think it should be ok. Im getting very frustrated and need help bad I have tryed 2 TBs but I only know that one worked before the swap the other came with the motor but they are the same when on the car. I dont know what else to do, im going to try to clean the valve on the bottom of the tband see if that helps.

 

did you swap for the same engine.
you have not tried new iacv, no ?

i had the same problem in the winter only - for about 3 winters - did not do it last winter (well, expect for 1 (only one) time))
but my idle does not increase when i turn on the AC.
when the iacv is activated, you should see 9 volts or more at the black/yellow (+) and green/black (-). this is for 84 to 91 model year according to haynes.
do you have those same colors. if not, did you know from the manual which one was pos or neg ??
there are other troubleshooting tech if you want them.

 

yes i changed for the same motor, and no I didnt put a new iacv on I tryed the one tha came with the new motor and the one that was on the old motor(that didnt have this problem) and I bought a used one of another car that ran fine, that is why Im scared to buy a new one for $350 Im in the process of cleaning one right now with carb cleaner and im clearing codes to see if it will come back. if any one has any other suggestions lets hear them.

 

i dont want to buy 1 either - bout 190 at autozone.

the following is for an 84 - 91.
Ignition off
1) measure resistance between the terminals. should be 8 to 15 ohms
2) should not be continuity to ground on each terminal.
3) turn ignition ON, measure voltage on the wiring harness. if there is voltage, the ecu may be faulty.
4) if no voltage, measue the voltage between the black/yellow (+) and ground. (note - the blue/yellow wire is the negative (-) wire.)
5) if no voltage, look to repair the circuit in the black/yellow wire between the eavc (iavc as we have called it) and the #14 fuse.

hope that it is the same for 92. mine passed all the above tests.
if yours does also, post back because i have more toubleshooting techniques that i found. (just short on time).
Hope this helps

correction to the above - applies to 1988 and later (Haynes was printed for up to 1991).

 

great info thanks

heres the results

1) there is 0.0 resistance between the terminals
2)there is no continuity btween the posts and ground
3)dont understand what to test on this one
4)12volts between black-yellow and ground


if you give a little more info on number 3 i will test it out, let me know what you think from here.

 

hope it is the same for 92 - think it would be.

i did not write it very good - and neither did the manual.

number 1 and 2 are referring to making a test of the iacv itself. so you need take off the ellectrical connector and get the leads of the ohmmeter into the recessed plug of the iacv (there are 2 prongs down in there).

Number 3 and 4 makes the test on the connector which has the electrical wires attached to it.
Since you disconected to do number 1 and 2, just leave it disconnected and turn the key to ON position. Make sure to change the VOM meter to volts DC. Number 3 is making a test when the iacv is NOT activated (do not have the lights or ac on when doing this test - should have everything off - so there should not be voltage at the connector).

i really need to know the specs for 1992 - since my manual only covers up to 1991. But if test number 1 is zero, and it should be 8 to 15 ohms, then i would say that the electrical part of the iacv is defective.

 

was the ohmmeter set on Rx1 for test number 1 ?

 

Im not sure I dont have the ohm meter in front of me but it was set right, and with every thing off and the key on the yellow wire had 12 volts,

 

is that re-doing (or should say doing #3 for the first time), and it shows voltage on the 2 wires coming into the connector - that should not be - assuming the 92 troubleshooting is the same as 88 - 91. that is saying that the ecu may be faulty.

in doing #1 - must make sure that the 2 leads of the ohm meter do not touch - will get 0 if they touch.

 

no the leads were not touching when I was checking the 2 prongs on the valve, I only have voltage on the yellow and black wire but not on the other, the other wire is grounded, what do you think? also do you know the part number of the iacv from auto zone? they quoted me 70bucks and that seems to cheap i dont think it is the right part.