Rep Power: 0

I'd seen this posted here in the distant past, but I don't think there was ever a resolution.

If I'm pulling away from a stop there is a brief drop in power, for about a second, when pressing the accelerator. Once it gets going, it accelerates as good as any 2004 Civic can, and will easily go up to any speed I want (which may or may not exceed Interstate highway posted speeds). It's not really harming performance, but it is a slight annoyance.

No codes. It idles fine. And again, acceleration past this short "dead spot" is still very good. And it had this habit before I replaced the cylinder head a couple of years ago (which included the usual timing belt/water pump/plugs, etc.), so it is not new behavior. It seems to be a little more pronounced when the engine is cold, but still does it most of the time when the engine is warm. There is also no delay if I have to punch the throttle while already moving--she gets up and moves. It's only from a stop when this happens.

My only two thoughts are that it is some sort of fuel starvation issue where the fuel system doesn't catch up to accelerator input fast enough, or it's a brief timing issue. If it were a fuel delivery issue, though, I would expect it to give me a lot more problems than this (inability to provide enough fuel to perform passing maneuvers or attain higher speeds, for example--both are solid).

Curious to see if it's something other owners or mechanics have dealt with.

 
Rep Power: 133

Use only OEM NGK spark plugs.
Air filter new?
Fuel filter clogged or weak fuel pump?
Run some fuel injector cleaner like Techron (the real stuff).
Check for vacuum leaks.
EGR valve and ports clogged?

 
Rep Power: 0

Just about everything listed was freshened up and cleaned while the head was off. New plugs, especially, since the previous owner had used some Bosch rubbish (one of them shattered apart in cylinder #2). I've used NGKs in Hondas since I owned an '88 Accord decades ago.

I never did check the EGR valve itself. The passages in the engine, when the head was off, were all cleaned out, and the new cylinder head was clean. No vacuum leaks that I know of, but haven't actually done a smoke test to find out for sure.

 
Rep Power: 367

cruise control? if yes, turn off and check?

 
Rep Power: 222

A/f sensor getting old and slow?

 
Rep Power: 0

Update--it took removing the cylinder head, replacing piston rings, honing the cylinders, and reassembling...

...to fix an oil burning issue. (It would use a quart every 300-400 miles and I'd get black soot out of the tailpipe. I've put ~500 miles on it now, and the oil level hasn't changed at all.)

After the first start, I got an error code that the idle air control valve circuit had an issue. I removed the valve, cleaned it well with carb cleaner, dried it out, put it back on, the code went away.

No more hesitation from a stop. I'm thinking it was the IACV, which was probably marginal before I disassembled the engine but was triggered enough to set a code once the engine sat for a few weeks unused. Anything else in the cylinder head and block I cleaned out while it was open--a little bit of crud, but nothing was blocked.

A tip for removing the IACV--it's held on by what look like Phillips-head screws--they are actually JIS #2 heads. My drill has an attachment that works as a light impact driver--using that, the screws loosened up immediately, with no damage.

 
Rep Power: 0

Well, it wasn't the IACV--it still hesitates during acceleration, more noticeable when cold.

Although I will say that after doing all the work above, I took the Civic from the Mitten State down to New Orleans, all the way up the Mississippi River to St. Paul, MN and back home, and had nothing more than a P0420 code. (I've since replaced the downstream O2 sensor, which did not look healthy from all the oil burning for 10k miles, but the cat may also be contaminated--remember, this was burning a quart every 300-400 miles). Otherwise the Civic ran great, got 34 MPG, and upon returning home with nearly 5,000 miles since the new rings, the oil level was about 1/8" below the full level on the dipstick.

I did notice something. The other day while the engine was still cold, an oldtimer pulled out in front of me at an intersection and I had to stomp the brakes. Taking off from the sudden stop, the engine hesitated quite a bit more than it usually does.

It makes me think this is fuel-related--it does feel as though the engine is a little fuel-starved during sudden acceleration. Apparently the Civic has three filters? There's the sock on the fuel pump, a filter on top of the fuel pump assembly, and a canister-style filter near the evap system. I'm tempted to replace the canister filter and the entire fuel pump, only because it's 19 years old with 255k miles on it and I'd consider it a preventative measure. I will probably take it on at least one or two more rallies this year and I don't need it failing in the middle of nowhere.

Once it warms up, I'll tackle it and see if that helps.