Most of the time my 2001 Honda Civic sounds like this...
Vrooooooom. But some times when I start driving it sounds like this...
Vrooom putt pa putt pa putt pa vrooooom. When it's in the "putt pa putt" mode, pressing the gas makes no difference. The amount of time it spends in "putt pa putt" mode varies, sometimes its a couple seconds, other times its as long as 5-10 seconds.
This always happens within the first 100 yards after starting the car, and it runs fine after that. It is not throwing any error codes, so if it's misfiring it's not reporting it.
What would be the likely cause of this behavior?
It only seems to happen after a cold start (car has been sitting for > 4 hours). The outside temperature does not seem to be a factor, it has happened in winter (0F-20F) and summer (70F-90F).
Spark plugs were changed about 3-4 years ago, but I will be changing them today.
Fuel filter might be original, or at least has not been changed in the 6 years I've owned the car. I am thinking of changing this too, but it is a pain in the ass to get to since it's in the tank.
Replaced spark plugs. The car seems to be running better, and have not yet experienced the reported issue (though it was very random, so it may be to early to call it fixed).
Spark plugs did not solve the problem.
The vehicle is also idling very low (200-300 RPM) once it's warmed up, and occasionally stalls while idling.
Just had the car to the dealer for a software update, turns out there was a service bulletin that mentioned this type of issue. The car seems to be running better, idling normally, and less hesitation when accelerating from idle.
Got a new error code that might help find the cause of this problem, P0420 Catalyst System Efficiency Below Threshold. After reading the comment on the answer to this question, I'm starting to suspect the catalytic converter. I did notice a leak near the manifold, so I'm not sure if that would cause the code or if the catalytic converter is really on its way out. Unfortunately the manifold and catalytic converter are a single unit, so I'll have to spend the ~$500 to find out.
Crushing the car and purchasing a new one, seems to have fixed the problem.