Ok, I have done searching on this before, and I found some stuff that seemed similar, but nothing that looked like the exact same problem, or nothing with a solution. I have had this problem for a while and it has gotten progressively worse. Besides this, the motor runs great, and there is no CEL. Whenever I start the engine cold, for a few minutes, it does not run well at all. Now, it has gotten so bad that when cold the engine struggles to start. It must kick much longer than usual, then once it starts to run, struggles for a few seconds to raise the rpms to idle position. The worst part is that once started, when I push the gas pedal, the rpms drop sharply before rising. They drop below like 500 rpm, and it feels like it almost shuts off, then they go up. It will run like this until I start driving it for a minute or so. Like once I get up and moving (and I must move off very slow the first time to keep from stalling) and I drive for a minute or so, then stop at a traffic light, the hesitation is almost completely gone. It still seems like the revs will fall a little before rising, but it is very small. When the car starts up warm on the other hand, it feels great. Like if I drive somewhere, shut it off, come back five minutes later and start it back up, it runs great. The throttle is instantly responsive, and it pulls so much harder. Does anyone have any idea what might be the problem? Any more details I can give to help pinpoint the cause?

Oh, and if it is relevant, I think the motor is from a automatic zc, because when I got it, it had a drive plate rather than a flywheel.

 

just a shot in the dark, but, my sohc zc used to do something similar, turned out my valve lash was adjusted too tight, fixed it and car started up smoother than ever...so i would check your valve adjustment

 

Try your EACV, its the small cylinder on the back of your intake manifold. This keeps the rpms up slightly higher when you cold start to get the motor warmed up, once it warms up the idle lowers. This is where I would start, if you have a helms look it up and if not theres a downloadable manual if you search. To get you started disconnect the plug going to it and measure the resistance, it should be 8-15, if not then it suggests to replace it and see if the problem gets better. After that you get into testing the ecu etc....

 

Thanks for the suggestions. I hope it does not have to do with valve adjustment. That seems complicated to fix, so I will try other suggestions first. Also, it does seem like it is an airflow/intake problem

About the EACV, I know my brother's f22 has an IACV and a fast idle control valve. Does the EACV basically replace and serve the same purpose as the fast idle valve? Or are the EACV and IACV the same thing? People seem to use EACV and IACV iterchangeably.

I do still have the intake manifold from my stock civic LX motor. Can I just pull off the EACV and try it, or is it different?

 

If your LX is a 4th gen (d15b2) then it wont work, the intake manis are different. And yes the EACV and Fast idle valve are pretty much the same thing. EACV = electronic air control valve. Id test the resistance to see if yours is working properly. I'm not sure if it can be "cleaned" but I do know theres a gasket and o-ring in there, if its not working its worth a shot.

 

EACV is reading a healthy 13.2. I assume I was supposed to measure it while the engine is off. What should I test next?

 

mine used to due this, timing was retarded @ the dist.

 

its not too difficult to adjust the valves, if you have a haynes manual, it will step you thru it, but yeah, id search for other easier fixes first, but that sounds like your car is doing exactly what mine was.