Issue came out of nowhere though.

IACV is new
TPS calibrated
No vacuum leaks (all hoses are new)
TB gasket and intake gasket like 3months old.
Coolant is bleed, actually I even bleed it again after it happened, was working fine before though.

Cold runs at 1800rpm and slowly going down to usual 800rpm +-50

Gets to operating temp, then if I slowly drive like 10kmh, press the clutch in, idle drops to around 1300, goes up to 1400 and sits there while I'm still slightly moving. I stop completely, few seconds later drops to 800rpm... It happens only at operating temp, the rest does its job as its supposed to. I have no idea where to look at, no codes, its DOHC ZC OBD0.

 

Unplug the IACV the idle should always drop to less than normal. If it does not, find out how the extra air is getting into the engine. The only way the engine can run fast is if it gets air. You could have a sticking throttle cable or other reason the throttle plate doesn't always close all the way when you're not pressing the gas pedal.

If unplugging the IACV causes idle to drop, that means that the ECU is commanding it to open too much. The ECT sensor could be flakey, sometimes telling the ECU that the engine is cold even though it is warmed up. This will cause idle speed to increase as it is programmed to do normally on a cold start. Ohm test the ECT or replace it.

 

Went out and bought new ECT, same thing happens. It keeps idle stuck at 1300-1400 depending when I press clutch. If I cruise at 2k rpm and press clutch in, it hangs at 2k until I come to a stop, wait few seconds and it goes down.

If I unplug IACV and drive with it unplugged, rpms are lower but it doesnt hang idle ... I'm lost, is new IACV defective?

I've read online and some people call it "rolling idle problem". How do I fix it lol? Throttle mechanism is fine, I even loose the cable a bit more but it doesnt change a thing. I'm lost. Please help.

 

Check your accessory belts/pulleys (Alternator, PS, AC) and make sure those are all functioning appropriately... I've seen some instances where an AC clutch won't engage/disengage properly which causes a floating idle since the engine load keeps changing.

Not honestly sure if that's what's going on here based on what you're describing, but sounds like you've checked most other aspects.

Edit: 600 posts

 

Dont have AC ... Alt and PS are fine ... It doesnt float, it gets stuck when wheels start moving and pushing clutch in ... Does moving wheels have anything to do with it? Reving engine while standing still, no issues, I start moving, let clutch out, press clutch in, idle gets stuck at whatever RPM I was at (e.g 1400rpm), I stop completely, including wheels, 2 secs later rpms normal... I have no clue whats going on.

 

Guys anyone?

 

Hanging revs when clutch depressed; but only when gear shift is in a gear - BMW M5 Forum and M6 Forums

https://www.carthrottle.com/post/rev...heads-hate-it/

These posts indicate the ECU could be to blame. Actually makes a lot of sense to me.

 

Its OBD0 DOHC ZC like 1989 ECU. I genuinely doubt it knows when its in gear ... Also it happens only when at operating temp, in between it does not ... I just thought of something, could TPS be the issue? Can I somehow connect it to multimeter and put it in the car and see if voltage stays high, maybe it doesnt register ... Also if I'm in gear and standing still, doesnt hang ...

 

just had the same problem , exhaust leak, baffles in muffler denigrated

 

I dont see how that could cause hanging idle or even raise in idle ... Nonetheless, it was as I first thought, TPS ... When I would release throttle, mechanically it would close however readings on TPS were at 0.90volts, and after few seconds it would drop to 0,48volts however it had weird spike in voltage as well. Took off of my buddys civic, worked like a charm.

 

thats what every one told me , but facts are facts , i had high idle, rev hang and surging , i bought a new axle back and new metal gasket and all my problems went away, it is what it is....

 

I cant freaking believe, problem is back even though I installed new TPS, it was fine for few days. Should I replace damn ECU?

 

My hondas have always had a higher idle while moving with clutch in or in neutral.

 

Does it shoot to 1800rpm when clutch is in and stays there even 10 seconds after you stop? Or does it run by itself in 2nd gear lol, I can completely remove my foot off of gas and car just keeps going at 1600 rpm...

I've gone through 3 IACVs, 3 TPS sensors, ECT sensor, and 2 MAP sensors. Still ***** and runs by itself after warming up.

 

Have you checked that it is not just the throttle cable sticking? Engine warmed up but not running, have someone press and release the gas pedal while you check that the throttle lever goes all the way back to the stop and the TPS back to 0.4 volts every time.

 

You mean 0.48volts? What makes no sense is, sometimes it drops normal, sometimes stick at 1400rpms, sometimes at 1800rpms, sometimes it keeps driving itself with no effort on my part, however after I stop and wait few seconds it drops to 800rpms, how do you explain that? I mean if cable sticks, wouldnt it just stick and not lower RPMs?

If I remember I unplugged IACV and drove around, no issues. And no IACV is new, something somewhere is telling it to be full open I believe. New TPS, new MAP, new ECT sensor. I ran out of sensors to replace haha. Anyones input is appreciated, cant drive it like this, I let of gas pedal and its still moving forward lol.

Edit : Again doing this only when warm.

 

Anyone before I burn some more money on ECU..?

 

after 3 years, did you fix the hanging idle problem? What was the culprit? I'm having the same problem as you describe, and I've already replaced one IACV.

 

I also have the same issue do you fix the problem? Please help us guys.