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Hello. I have a Honda Civic EJ9 with a d14a3 engine. So i got a new 90 hp P3Y ECU. Mounted it .. but the engine does not starts. Help please

Please introduce yourself in the right place...
This is a forum ! Cheers

i just need your opinion about my problem. why this is not the right place to do this?

You can introduce here :
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For users to know you, your car etc...
It is normal on forums.
BTW, did you change ECU to get 90hp?

Fokerix the difference between the 90hp D14A4 and 75hp D14A3 is mainly the restrictive throttle body gasket. It reduces airflow and therfore power. Yes they do have different ECU's but to gain the 15hp you need to change the gasket.

I would say put the old ECU back in and see if it starts. If it does then you have probably connected something wrong when swapping. If it doesnt then you will have to wait for someone else to help because I don't know... hehehe

What year is your car and what year is the D14A4 ECU from?? Maybe theres an issue going between OBD2a and OBD2b?

The problem is the immobilizer.
The new engine ecu needs the proper keys and immo ecu.

Yes it is the immobilizer that does not accept the key.

Throw away your 90 bhp ECU, put back your old 75 bhp ECU so the car works again. To go from 75 to 90 bhp just change the Throttle body gasket for a 90 bhp version which is paper instead of steel and has a 55mm hole instead of 27mm. You'll have instantly 15 hp more and don't worry about the ECU, differences are minimal performance wise.

Still i don't think the gasket gives right away 15hp more. I can think of 2 possibilities. Whether the performance difference isn't that high, or the ecu does make a bit of a difference. If we had the same ecus meaning same a/f ratio this would mean that the a3 versions would run extremely rich right? If it is balanced in a proper way then by increasing the t/b opening via the gasket change then it would run lean or maybe i would say so lean as to be more power productive. What are your thoughts in that?
Have we ever dynoed a stock d14a3?

If you remove the 27 mm gasket and place the bigger one, the manifold pressure would change. 27mm is so small that the 75hp engine's manifold may not see close to atmospheric pressures at WOT like 90hp version does, atleast it would have a lower value. So in a 75hp engine with the bigger gasket, the manifold pressure would be closer to atmospheric and the MAP sensor reading this pressure would result in ECU refering to a higher load coloumn in the ECU mapping.
I'm thinking that the gasket replace wouldn't affect A/F badly but this should definately be tested by a wideband sensor just to be sure.

Guess you're right too.. Gasket should be the only factor. or the ECU is different?