I have a USDM 1990 Honda CRX DX that now has a non-USDM D15B (OBD1, MPFI, VTEC, SOHC, P08 head & ECU). The conversion was a nightmare in that three different "mechanics" had their hands on it over 5 years. I was too patient, I know.

The car is driving as my daily driver, but there are some concerns pertaining to the conversion. I know little-to-none about wiring, and if it were not for my shop manual and the Internet, I'd be spending a fortune at shops for tiny problems.

Here are my current concerns:
Since the engine & head & ECU are the P08 (yes, I know the D16Z6 also had a P08 head), and the body & engine harnesses are my original CRX DX (OBD0, DPFI, PM5 ECU) that were converted (possibly correctly), AND since the car drives well and, if not for my CEL codes (1 & 8 & 21 & 22), all is fine...

What should I do to ensure that I am taking the best car of this unique/rare engine?

Like, even though I'm able to drive it, what is a common problem that is made during conversion that can permanently hurt the engine?

I see that some wires are not connecting to the ECU, and that some of the wires on the ECU plugs are cut near the plugs, and that my VTEC OPS is not connected... (Can I safely operate the engine without VTEC connected as long as I keep it below 5500rpms?)

I'm not done troubleshooting the O2 sensor (code 1) and the TDC sensor in the dizzy (code 8), but if it comes to having to replace both, so be it. It's odd to me that my engine is running fine and I have a code 8. Every forum post I have seen (that had responses) that had a code 8 were also not able to drive their car. Anytime someone said "I have a code 8, but my car runs fine", people would still respond with "replace dizzy".

Speaking of O2 sensors... I could never find out if my single-wire runs on the 0-1V scale, thus allowing me to connect an air-to-fuel ratio gauge to it. Are all/most/(or just the single-wire) Honda O2 sensors 0-1V?

Eventually, I will want to have more feedback from the ECU, and instead of chipping my rare P08, I was getting the impression that I could chip a P28 specifically for the D15B, and then add feaures, such as Bluetooth and custom ROMs. I hope to be able to select between "fuel efficient" and "power" maps via Bluetooth, but I can understand if this is not possible until OBDII.

I truly apologize if I have made anyone facepalm while reading this.

If you do respond, please do remember that this D15B is the P08 (1992-1995 OBD1, 2-stage VTEC) and NOT the P2J (1996-2000 ODB2, 3-stage VTEC).

Thank you!

 

1) Oxygen Sensor "A" (Primary)
8) TDC Sensor (Top Dead Center)
21) VTEC Solenoid Valve
22) VTEC Oil Pressure Switch

1) O2 sensor isn't run correctly most likely. OBD1 requires a 4 wire O2 for the ECU. It probably isn't hooked up or it is a bad sensor.
8) Bad distributor most of the time. Could be a sensor loose in the distributor. Could be the wires leading to the distributor being run improperly. Check the pin outs on the distributor and make sure they are ran to the ECU. Additional wires are needed for MPFI compared to DPFI and the swap could have been done wrong.
21) Most likely not hooked up. That and check that the solenoid clicks when 12V is ran to the wire. Could also be a dirty screen. It is part of the gasket, $20 fix most of the time.
22) Same as above. Except don't run 12V to it. It is most likely not hooked up or not grounded. That or the screen again.

Not wiring sensors. Wiring sensors wrongly, backwards, ect. That and improper torque specs.

You need to do some research on this one. The P28 can be chipped to run the engine in your car. It could probably do it stock since it is for the D16Z6, which is similar to the D15B. You can get multiple tunes and a ZIF socket to change them on the fly. Just do some research. You won't see much gains in Hp or fuel efficieny out of a stock D15B.