I just had the engine swapped im my 99 honda accord EX. Old engine valve seals went. After changing the engine I noticed that the car wont go passed 4000RPM's like its cutting itself out.
We changed the vtec chip? from old engine to see if that would help but no.
I also noticed that i dont get the gasmileage i used to. (400mi to tank down to about 340mi per tank)
There is a gas smell when i turn the car on and when a/c is on idle keeps waivering, going from 850 to 1200(morer noticably than before).
Also, the radiator fan is now constantly on, never shuts off.
Dont know if all these problems are related but I have already sunk in alot of money into this car and need this fixed. Please help and tell me its a simple fix!!
Thanks!

 

Got your answer - you have the water temp sensor and the vtec oil pressure sensor backwards. This is why the fan comes on right away - the VTEC is ground switching the fan on. You will also notice on pin 10 of socket C of the ECU (VTEC oil switch signal) measuring about 6 volts - this is the ambient temp voltage from the temp sender. Anyway, swap these two connectors - same size, # of pins AND right near each other.

You should be getting a P1259 code caused by the 6 volts on the VTEC pin. You will notice even when you clear the code, it comes back without even starting the engine.