I'm going to explain this to the best of my ability... when my engine is cold it runs like a champ. No hesitation or anything. After a while of driving/warmin the motor up, the motor seems to hesitate frequently when I get on the gas. It will eventually let loose and go... but at first there is ALOT of hesitation. You can feel it holding back... I'll just list the specs of my car, along with mods I did in order to solve the hesiation issue (which obviously didn't work)....
99 Civic EX
96 JDM B18C motor w/ LSD tranny
OBD1 P72 ECU

Replaced:
Fuel pump w/ Walbro 255 pump
Fuel line from filter to rail w/ GSR line.
Brand new altenator and battery... didn't think this would help, but I needed them

And just some more specs in case you are wondering...
I pulled my a/c and power steering(side note)
Replaced spark plugs, rotor and cap.
Also, I replaced the internals of my stock d16y8 distributor with the gsr internals so it would plug righ into my stock harness.
I am running very rich..lot of carbon in the exhaust pipe.

Any ideas?

Thanks!
Matt

 

what kind of exhaust are you running?

 

is your cat shot?
did you do a compression test?
changed the oil yet?
PCV valve changed?
do you have exhaust leaks?

 

Check the timing also, when i did my swap i completely overlooked this. My timing was way retarded, when it was cold it ran like a champ also, when it warmed up anything under 6 grand it was shit. That would be my first guess

 

Maybe the guy that wired your IABs was drunk?

Running JDM engine off of USDM ecu...

-PHiZ

 

my friend is running a JDM d15b engine off a USDM d16y7 or y8 ECU.. needless to say.. his vtec no longer works and his engine is quite strugglish...

 

I had a similar problem with my swap. I received alot of hesitation, very jerky throttle response unless I gave it a load of gas. It ended up being that my TPS - Throttle Position Sensor was faulty (Might also be called TAS - Throttle Angle Sensor) After replacing that, I had very smooth low rpms. Although, I don't see how running hot/cold has anything to do with that. Could also be that you might have your MAP sensor and TPS hooked up backwards. Check your plugs and let us know.

Ugh

 

What do u mean by hooked up backwards? The map plugged into the tps and vice vs.?

 

Correct... I did this during install of my first swap

 

HMmmm.... I have no idea? I had someone actually drop it in and connect most of the connectors. How can I tell? Where are these two sensors located? Pics are always a big help I can try to swap them. IT does sound like they can be mixed up.