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Discussion Starter #1
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 reading I 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 the O2 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.
 

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Well it is not an injector problem cuz it would misfire after 3000. Try a different ecu if youy have one or borrow a buddies.. The ecu could be the problem!
 

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may be a stupid question but did you reset the ecu after you installed new o2 sensor to get rid of the code?
 

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injectors having a resistor box or not doesnt have anything to do with the ECU it just depends if u need a resistor box or not.. u dont need one so your good homie... the miss and the rough idle sounds like every other car with a 02 sensor code thrown that i have ever seen.... so yes try another ECU and maybe even look into a chipped ecu that has the O2 sensor turned off.. then u need to start tuning, first start with trying another ECU and if need be ask more questions.. good luck...
 

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Discussion Starter #5
Does anyone know if the pulsewidth put out to the injector from the ECU (OBD 0) has a different profile than a OBD1/2. What I'm wondering is if my OBD 0 ECU that is designed for the injectors that use the resistor box have a wider pulsewith than an ECU that doesn't use the reistor box. If this is the case, am I running rich on the low end of my RPM range and after I get to highway speed I've already had the CEL light come on so it runs with a miss. Does this make any sense? I guess what I'm wondering is if I need to go ahead and wire in my resistor box and put in a set of old style injectors to match my OBD 0 ECU.
 

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it has absolutly nothin to do with the injectors...i had the same proplem with my mpfi conversion. first i did the coversion with my stock motor i just changed the manifold and ecu added the resistor...etc. and everything i used was from an 89 si crx so there was no mismatching...i had no codes at all...as soon as i changed the motor when the original blew on me with a 95 motor i started getting o2 sensor code...no matter wut i did i got this code i bought new o2 sensors i went and got oem o2 sensors nothing worked...dude everything u described my car did....the problem is not the sensor or the wireing its the motor! your useing an obd 0 computer on a motor that was ment for obd 1/2 the emissions comming out of the motor is totally different and there is a big difference between a obd0 o2 sensor and an obd1/2 4 wire o2 sensor....the obd 1/2 has a self heating element that work with the motor hence the extra wires...the obd0 doesn't...basically invest in an obd0 to obd 1
conversion harness, get and obd1 ecu and 4 wire o2 sensor...as soon as i did this...bye bye...check engine light....the car runs beautiful vtech and all
 
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