I have a 90 HF w/89 Si ECU. I want to put on a 90 Si Head and Intake. I already have the Si TB w/TPS, Manifold, fuel rail. I hooked it up with the HF EACV, HF resistor box and injectors, and the EGR disconnected with the Si sensors wired in. It would not idle and generated a check engine light. I am curious if I need to get an Si harness. My manifold has EGR on it and the Si does not. Also the idle control appears to be different and requires wires that I do not have in my HF harness. Anyone help me on this?

 

Ok, check this out. I cannot tell you how to fix your problem. But I can relate. I had a HF that did not run. I had a blown motor in the back yard that still had a good head. The HF motor is an eight valve motor, and the si is a 16 valve motor. This is not a problem, despite what I have read here and on other posts. I tried it anyway, and the head bolted right up, and so did the intake manifold, and the exhaust. I put the timing belt on just Like I would have any old d-series. The car started right up, but Idled really high, like three grand. It ran good, ad I think in the shape of the hf pistons and the small combustion chambers of the 16v head, it made a high compression monster. The car ran like ****, but it would throw you back in the seat. The car idled like crap, and after a few minutes sitting ther, it would over heat. This is what i figure.

1. There must be a difference in the water pasages on the two heads.
2. Base cam timing on the two motors are different.

This is my advice, don't do it.
I did it just tosee if it would work, not to drive everyday

 

Thanks for the feedback! I think I will go for the whole Si engine swap complete w/harness. Either that or save up for a ZC or B series. Thanks again!

 

After I do my ZC swap I'll have a Si motor sitting around. It will probably need a new seals to be safe, 216K miles, but other than that it still puts be back in my seat whenever I want.

How far from TN are you?

 

the hf harness is fine I used it for 3 years on my b16a, you need to find out what code you have, then go from there it might be something simple.make sure you did not swap something like the air intake temp, and iac, also make sure injectors are in right order. check the code it will point you in the right direction, Jason