I have a 1991 civic and I can't get it smogged because the idle won't go below 2000 rpm until it warms up then it surges. Any ideas what the problem could be?

Disconnect the Idle Air Control (IAC) valve and reset idle to specs. Idle screw is "leaded in" on the throttle body end. They don't want people fooling with it. Just dig it out. Find the blue wire coming from the distributor, which is in the bunch of wires near the clutch, and attach a tachometer and set the idle speed to 450 rpm. Engine should be warmed up first. Reattach IAC valve and you should be set. If that doesn't fix it, you may try cleaning or replacing the IAC valve.

.. my friend had a problem with another car that was the same as yours. All he had to do in the end was change the idle speed. Hope it helps. Though I may have just said what txgreasemonkey said lol *s*

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Originally Posted by txgreasemonkey

Disconnect the Idle Air Control (IAC) valve and reset idle to specs. Idle screw is "leaded in" on the throttle body end. They don't want people fooling with it. Just dig it out. Find the blue wire coming from the distributor, which is in the bunch of wires near the clutch, and attach a tachometer and set the idle speed to 450 rpm. Engine should be warmed up first. Reattach IAC valve and you should be set. If that doesn't fix it, you may try cleaning or replacing the IAC valve.

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Txgreasemonkey, I have a 91 honda civic 1.5l which is idling at 3000 rpm. It was idling perfectly fine the day before (~1000 rpm) then the next morning when I started it up, it started idling at 3000. I had a coolant leak which was confirmed by three different repair shops, as being a defective (leaking) water pump (I was also told that fixing the coolant problem would fix the idling problem as well). I just finished changing the water pump and timing belt (thank you, Honda engineers!) two days ago, but it still idles very high. Also, when shifting between gears, it revvs up to between 3000 and 4000 rpm and does not go back down to normal rpm until I begin to release the clutch pedal.

I tried following my Haynes manual's procedure of disconnecting the EACV (IAC valve) 2P connector, then starting the car and adjusting the idle speed screw. The problem is, I don't know exactly what you mean about the screw being "leaded in". My idle speed adjusting screw is just to the right of the throttle cable and directly underneath the top of the throttle body and faces toward the engine. I had to pop off a small protective rubber cap and it's a philips head screw (the head is painted yellow) underneath with a spring around it. When you say to "dig it out", are you referring to somehow prying it out of the throttle body? In my case, when I turn the screw in either direction, there it no change in the idle speed. Please excuse my ignorance, but I simply do not understand what I need to do to make the idle screw adjustable. Also, where is everyone getting a tachometer from? I have called around to all of the auto parts stores here (Auto Zone, Advance Auto Parts, O'Reilly Auto Parts) and neither store has one. I don't have unlimited income for fixing this problem, so any and all help would be greatly appreciated.

Thanks.

Ezbless,

I have some what of a similar problem, 90 honda civic DX 1.5L DPFI, High idle and surging all at once (hot or cold engine) and only the O2 sensor code on the ECU. Almost like a sticking throttle position sensor. I can unplug the EACV/IACV and surging still occurs but idle drops. My idle screw movement did not effect the RPM. You can buy a digital timing light which usually have Tachometers built into them. Another sugesstion is to check throttle cable and if vacuum leak occurs. Another thing I found out is the mixing and matching of the Air Temp Sensor and EACV (they are typically right next to each other) 2P connectors, which are the same type but serve a much different purpose. I had accidentally plugged one in the other and it caused surging idle problems. I can't solve my O2 sensor mystery nor the surging.

Hey people I need help with my civic it's a 91 si it has a dx motor d15b1 motor with a d16a1 fuel injector its idleing 7000 an it stay at 7000 help ***

Slepylacc, check the throttle cable. It's probably adjusted too tight--back off the rear nut and then retighten the jamb nut.

Check your IAC... Mine had no gasket on it, so it was sucking in air around there and making it surge. Put on a gasket and no problems.. It might also be that the IAC is bad..


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