I recently did a dpfi to mpfi swap on my 1989 hatchback. All of the info I found on this forum made it really easy to get done. First off let me tell you about the parts used. I bought a 2000 model d16y7 engine and a 1989 mpfi intake without a fuel rail on it. I found a ps9 ecu that I modified for use on my manual trans car. I did the conversion but instead of using a set of injectors off of a ealy model I used the injectors and fuel rail off of the 2000 model motor. In all of my readingI found that I wouldn't need a resistor box with these injector. Everything went fine on the wiring for the ECU and once I added the ground strap back on to the engine she fired up and ran. The problem is that after it runs for a few minutes the CEL comes on. It is always a O2 sensor (1 blink) code. I replaced theO2 sensor in the process of trying to trouble shoot this but it didn't help. It never starts up with the code but soon after the light will pop on. Is the OBD0 ECU causing a constant rich condition due to the mismatch with the new style injectors? The car gets excellant mileage on the highway (42- 48mpg). But in town it only get 25 mpg or so. The only major problem with having the light on is that it idles poorly and you can feel a slight miss when you are out on the road. Under accelation it runs like a bat out of hell. I'm hoping that in fixing this that it will (a) improve my mileage (b) get the idle smoothed out (c) get rid of the highway miss.

 

Hmm, I thought you needed a resistor box. where did you see that you didn't?

I also have a code 1 that I have been trying to track down. I know it calls for "check oxygen sensor, heater, and circuit", but I have a sneaking su****ion that it's the IACV. I think that one uses a 2-wire and another uses a 3-wire. Make sure you have the right one.

 

All older Honda injectors used the resistor box. It has to do with what impedance the injectors are. That's why you don't see a resistor boxes on newer cars. I think they changed from high to low impedance injectors around 1993??? As far as the IACV it was a 3 wire on my DPFI and the MPFI. It also only has a single wire O2 sensor. I've got a feeling it may have to do with a differencein the pulse width that the PS9 puts out. The PS9 is calibrated for high impedance injectors that need a certain pulse width and the newer low impedance injectors need a slightly different pulse width. I'm hoping someone can confirm or dispute this so I can get itrunning 100%. Thanks for the reply