I have done A LOT of research trying to figure out a problem I've been having and can't seem to narrow it down.

I have a 2000 Honda Civic EX with the stock engine and 5 speed transmission. For the past couple months, after starting it (usually when the engine is cold), the throttle will lack response upon the first "launch" so to speak. Let's say if I back out of a parking spot, and then take off, when I start to actually get on the gas a good amount there's very little response and if I keep my foot steady it will suddenly launch after a second or two. I've replaced the distributor cap and rotor, fuel pump, O2 sensor, and some other parts recently. I know my cat is rotted out and I have an exhaust leak at the donut gasket between the exhaust manifold and cat. I am rather unsure of what could cause this problem, as it idles steadily around 600 RPM when warm, like 1000-1400 when cold. It does not miss or run funny, but occasionally seems like it lacks low end power at certain RPM. Normally the "lag" happens when it climbs to around 3k, which is also around where it feels like it lacks power occasionally.

If you have any ideas of what I should look for or need more information I'd greatly appreciate the help, it's just getting really irritating because I don't know where to start. Only mods to the car are a catback exhaust, a 12 lb flywheels and an ACT clutch. Thanks in advance

 

I had a similar problem (hesitation, and more so when cold), and new spark plugs and spark plug wires fixed the problem. I'd take a good look at the plugs and wires and see if there are any obvious signs of wear/ damage.

 

Sorry for the very late reply and thanks for the input. I changed the plugs and wires this morning and it seems to be running perfectly now and MUCH stronger. Plugs were clearly old, gap was pretty well out of tolerance on all plugs. Thanks!!