So I had a spare HF engine laying around. I decided to put it in my spare civic si. I looked everything over and determined it was all the same. So I threw it in and tried to start it. It turned over just fine. Except that it would stumble/jerk a little. Not normal for the hf motor that was just running a few days prior. Another thing I noticed. The place where the Si's map sensor is that hf's is a little different. So I put the HF map sensore/vacuume hose box on and tried to plug it in. I believe the map sensor plugs in but the other connector is 4 wires for the HF but only 2 for the Si. And one final thing. When I put the key on accesories the injectors stay on. Really weird. Does anyone know if there is a difference in the wiring going to the ecu? Or anyone know what problem I might be having?

thanks.

 

what engine harness are you using? - HF engine harness won't work in the Si car

 

So I would need to use the Si wiring harness? What about the HF's egr? If I used the Si's wiring harness the egr wouldnt hook up. Also the question still stands for the map sensor. And would I need to use the HF Ecu or the Si's?

 

you will need to use the Si engine harness and run additional wiring for the EGR valve lift sensor - the MAP connector should be o.k. - what is different is the purge control solenoid - on the Si, it is a 2-wire connector and on the HF it is a 4-wire connector that combines the 2 wires for the purge control solenoid in the control box with the 2 wires for the EGR control solenoid in the control box - in order for the EGR to work, you need the HF ECU

 

Yes you must run the HF ecu and you MUST use your original car harness.
Any additional sensors get ran straight to the ecu.