valos

I've been having this strange issue with my '01 Civic for the past 6 months and I've done just about every likely replacement to fix this issue to no avail. If anyone can suggest what this might be, I would appreciate the feedback. Basically, the car starts up fine and drives fine after about 5-10 minutes (when warmed up). The problem occurs BEFORE it warms up or while its warming up. At startup it might have a rough idle for a bit, then the RPM goes up unexpectedly (w/o touching any pedals), and when I put it into reverse or forward shift and press the gas, the car does not want to go. It goes and then without my control just stops and rough idles, then might go for a sec again until it unexpectedly almost "stutters" and rough idles again (but the engine does not die). The whole time I can be pressing the gas all the way and the engine revs correspondingly but the car just does not go.This process can repeat several times until the engine warms up, after which point the issue disappears. The check engine light USED to be on and the code was for a bad catalytic converter. I changed that, the light went off, but the problem remains. Changed the spark plugs, air intake valve, and cleaned out the intake, none of which solved the issue. I feel like the key to solving this issue lies in the fact that this occurs only during a cold start (even just 20 minutes after shutting off). I'm trying to sell the car but the problem scares people away obviously...although the car runs great once warmed up! Any suggestions? Thanks!
My next possibilities:
fuel filter?

JDMswagSerf

The movement sounds like a transmission problem.
The idle is something else.
I'm assuming its AT?
How does the reans fluid look? Color? Level?

valos

yeah its AT. Last time I checked the fluid, there weren't any issues... but I will have to double check on that for a more recent update. Would a trans problem be making a noise that sounds like "pa putt pa putt pa putt"? lol It makes that noise when it won't go, but like i said it goes away soon after. When the issue wasn't too bad (like 5 mos ago) some fuel additives seemed to have helped for a bit of time

JDMswagSerf

Fuel additives helped the car move when cold?
The noise you describe,mis it a clunking noise?
where do you hear it coming from?

valos

Fuel additives used to make the issue disappear altogether for a few weeks. Since then, its gotten worse and this doesn't help anymore. The noise I hear is not a metallic "clunking" type of deal. It is actually more of a sputtering that comes from the underneath mid-rear area. Imagine the noise something makes when its clogged. Might it be the fuel pump or filter?