I have started threads with this information on Honda-tech in the Prelude and Tech forums and am not getting much response.
http://honda-tech.com/zerothread?id=2047513
To recap what was already stated in that thread:
1. Did an H22A swap into a 92 civic CX. I made entire engine harness myself using the connectors from the EG harness and H22 harness.
2. Since starting the car for the first time I am getting a CEL 3, which represents an electrical issue with the MAP sensor. The car runs very rich, which is causing the idle to bounce slightly.
3. I have tried 3 different Honda MAP sensors. They all do the same thing. I measure 5V and GND on the outside leads and the signal lead measures approx. 3V at idle, which is about right.
4. I have replaced all of the vacuum caps to the IM. Some of them were cracking from age. I also replaced the hose from the IM to the MAP because it wasn't as snug as I'd like. If there is any kind of vacuum leak anywhere else, will I get a CEL 3?
5. The wiring has been tested. With the MAP sensor connected, I get 5V, 3V and GND on the leads at idle. With the MAP disconnected, I get 5V, 30mV and GND with the engine off and key in the ignition position. Continuity from each of the 3 leads from the sensor to the ECU pins is good. I have less than 0.01 ohms on each wire. They are pinned in the correct orientation.
6. I have replaced the original P13 ECU with another good JDM P13. I get the exact same CEL, bouncing idle and rich condition.
At this point, I have gone completely through the Helms CEL 3 troubleshooting procedure. There are no other suggestions after replacing the ECU.