I cannot figure out what to describe it as OR find a reason as to what is causing this problem. What happens is, at regular road speed( any speed from 40-65) at 3-4,000 RPM my car starts to buck slightly but noticeably at part throttle, if I floor it, it will not do this. It is especially noticeable on a smooth freshly paved stretch of roadway. The shop I take it to seems to think it is a question of it seems to be running lean. I have checked the distributor, throttle body( and related sensors), loose connections, low coolant level( there is plenty of coolant), low oil( I have enough as I changed the oil 2 months ago), I even seafomed the intake and upper cylinders, changed plugs and wires 3 months ago, and I only use Shell V-Power 93 octane fuel. The engine is a B16B with a modded P28 ECU. Also, I cannot seem to find any vacuum leaks. Even stranger, is this only happens if my car is cold. After I have driven it and it warms up, it does not happen.

 

BUMP

 

this happened to my old civic with a z6 it ended up being the coil in the distributor was on its way out. If some one has the same engine as you swap dizzys with them to be sure. Also your dizzy could be out of tune or make cap/rotor is dirty with the white stuff inside or cracked. also long shot but maybe your inline fuel filter is dirty. check thoose for now.

 

so it happens at partial throttle and goes away when you floor it... then it goes away all together when it warms up. in other words you have a stutter in open-loop when the engine is cold.

by modded ECU i assume you mean chipped... if so pull the jumper off the board at J1 i think.
see image here
[thanks Honda Tuning Magazine!]
that basically toggles between the burned chip and the factory chip. see if running this way has any effect on the issue. if so consider a change or retune of the ECU.

 

yeah always good to confirm all ignition components are in good working order before continuing with running problem troubleshooting.

good call Dave.

 

I will check the fuel filter tomorrow before work, and on Saturday the cap and rotor it is, thanks

 

Had this happen on a Prelude. Rotor was coming loose.

 

Well, I checked everthing at lunch and I noticed that it now does it when the engine is at regular operating temperature, only at 4k rpms though. Everything checked out when I looked at it. I probably could stand to change the plug wires as they look like they came with the engine. I will replace the cap, rotor, plugs and fuel filter before I go into anything else.

 

Well, I don't think that would be too smart as I have a B16B swapped in at the moment

 

BUMP, any other ideas?

 

had this prob....turned out to b the icm going bad...only did it around 3-4k