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Ok so I have been on the internet for about a month trying to find anything on this problem. I have a 99 civic with a d16y8 and 5 speeed that is stock other then a short ram and a b16 TB. the car has 157xxx on it and has been a great car to this point. First let me say there are no codes and no vacuum leaks that I can find. I have replaced the IACV, bled the system, and performed the idle learn procedure. The problems are a high idle (1500-2000 RPM) and an extremely high coasting idle at 2500-3000 RPM. I will try to post a clip as well. I just need to know what I am missing here. I have to have this car as it is my only “reliable” transportation. Also I need to adjust my valves but is that enough to cause this issue?
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Well I have adjusted the cable to have about 1/2″ of play. The cable also seems to be in the correct spot. Also when I drive at highway speeds for about 45 minutes or so it will coast at the 2500-3000 rpm but once stopped it actually idles around 800 rpm.
Do you have live data to see what the ECT sensor is reporting?
Also fuel trims, and does the car have an IAT sensor?I actually just went to a buddies place today and got some data from his scanner. This is all at operating temp btw. IAT read 131 degrees ect was 180 to about 205 degrees. The LT fuel trim was at about .9 to 1.1. I do not remember the ST trim. The LT trim is high isn’t it?
The LT is not bad. The IAT is a tad high but probably OK. Might be worth checking its resistance against specs.
Also if I block off the hole to the iacv in the TB it will drop in rpm but stay running. And if I unplug the sensor it runs like it should. No high idle or coasting issues
Aftermarket. I bought it from rockauto.com
I use them alot and never have gotten a bad part. I have another factory one off an old intake manifold should i clean it up and try it?If you had the same symptoms before swapping the IAC, then the IAC is probably not the problem. However, no harm in trying out the spare OEM if you have it. Also checking all passages to/from the IAC would be good, as well as checking the wiring to the IAC.
Something else worth checking out would be the fast idle thermo valve.
I don’t have a FITV. And the symptom was different before the iacv swap. It was a bouncing idle. I’ll try swapping the sensor out tomorrow and I’ll get back to you.
Well I couldn’t use the sensor I had because the plug was in the wrong posistion. I decided try put the original sensor I replaced on the car and it freaking worked… so far it is driving nice after I adjusted the idle. It still revs high when coasting in neutral but only to 2k which is way more tolerable. The only thing I can think of is maybe the pcv is sticking. Either way I have one that I am going to change soon.
Alright so need a little more help. So since my last post I cleaned the original iacv again and reinstalled it. No bouncing idle but still had the high coasting idle. When I used my buddies scanner to get some data when I put the car in neutral and coast it says the iacv is at 30% and once stopped it goes down to i think it was like 4% and it actually idles very good now at about 800-1k. I then decided to clean my wheel speed sensors and that actually dropped the coasting idle from 2500 to 2k. Problem is still ther however. So I’m looking at maybe the vss being bad? My speedo doesn’t read until I’m going about 10-15 mph. Can a vss cause an idle issue? Also is something commanding the iacv to engage? I am kind of leaning toward a faulty ecm?
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