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Another write up- not done by me. Mine is going to have COMPLETE details as described in another post I made on this topic. I do have this complete write up and pictures available if you need to have it let me know.


Multi Point Fuel Injection Swap.... (MPFI swap)

I hope this will be the "end all" for most of the MPFI questions. There are many sites devoted to the swap, but most of them are lacking in information, or vague at best. I recently did my swap and took the time to photograph and document all the steps. This write-up assumes you are mechanically inclined, and have the proper tools and know-how to complete the swap. It also assumes you have some kind of manual (Helms, Chilton, Factory, etc.) to reference to for torque specs and other info. Neither the Alternative Honda board nor myself can be held responsible if you hook the wires up wrong and fry your ECU. If you have doubts about your abilities.... have someone else do it. If anyone sees anything different than their experiences PLEASE post your experience... I am fully open to constructive criticism and will adjust accordingly. With that said, here goes...

Step 1: get all the parts

You will need the following parts for the swap. All of these parts are available from any MPFI CIVIC/CRX made between 88~91 (refer to Fig. A)

1: A complete MPFI intake with throttle body, injectors, harness, and related hoses and fuel lines (see "A" in the picture)
2: A PM6 ECU ("B" in the pic)
3: A distributor with the cylinder sensor ("C" in the pic)
4: A resistor pack for the injectors (found on the drivers shock tower, Grey box next to "D" in the pic)
5: A coolant bypass hose for the Manifold to block (shaped like a question mark, not pictured)
6: A new intake manifold gasket.
7: Approx 7 feet of shielded 2 conductor wire
8: Assorted color wire (18 gauge) for running injector wiring and extending TPS sensor
9: A 2 pin Molex plug or similar connector (for fast Idle Solenoid)


Step 2: remove the old DPFI intake

This is an easy step and I won't provide all the details you should already know, except to remind you of the following....

1: drain the radiator first... on the DX manifold there is a coolant line running inside the casting.
2: don't forget the bolts on the bracket below the intake manifold (on the bottom of the manifold, next to the oil filter.)
3: When removing the fuel line, release the pressure first with the 12mm bolt on top of the fuel filter outlet.

Step 3: engine compartment wiring.

A quick note:
I soldered all of my connections and used shrink tubing. You may use butt connectors, but do so at your own risk! This section also assumes you have both sides of the plug for each of the components.

Beginning with the injector harness:
There are 8 wires on the injector harness. Find the four same color wires with the black stripe. (either red or yellow as the base color) These will need to be wired to the resistor box. Add a length of wire to each of the four, long enough to reach the resistor pack on the shock tower. On the injector resistor pack there are 5 wires, one red and four black. Splice the red wire into the large Yellow/Black wire in the engine harness plug next to the shock tower... or tie it into the large power wire (also yellow/black) that fed the DX main injector (brown injector plug). Attach the four black wires to the four striped wires (red/black or yellow/black...) from the injector harness. The other four wires are solid color, and are colored as such... red, brown, light blue, and yellow. These are the injector wires to the ECU. Add approx 7 feet to each of these wires, preferably of the same color to match each one, and tape the 4 of them into a loom. Take these 4 wires and route them through the firewall and towards the ECU. We will hook these to the ECU later.

On to the Distributor;
Take the Si Distributor and find the blue/green and blue/yellow wires on the plug. Attach these wires to the two conductor, shielded cable you bought. (you did get shielded, right ?) Pay attention to which wire went where for future use. Replace the DX distributor with the new distributor and run the shielded wire through the firewall and to the ECU. There are 5 wires left on the distributor that will need to be spliced to the DX harness. The wires all match in color and you can either cut and splice or swap pins. You will notice their are two white wires. One is for the 12V + feed to the igniter module, and the other is for the crank angle sensor. The crank angle wire will be in a shielded cable along with three others, and the igniter feed wire is outside the shielded cable on it's own....

Modifying the DX harness;
The main harness runs under the manifold and contains the EACV plug, Fast Idle solenoid plug, Intake Air Temp plug, and TPS plug. We won't need the old injector plugs from the DPFI set-up so you can tape or zip-tie those off. (Although you can use the yellow/black wire on the brown injector plug to supply 12 volts to the resistor pack...) If you take the time to remove the factory tape and split loom, you can then separate the differing plugs and get all of them to reach with the exception of the TPS plug, this needs about 12 inches added on. IMPORTANT: When you extend the TPS plug be sure to swap the outer two wires (green/white and yellow/white)... the DX TPS is backwards from the Si and if you don't swap the wires, the ECU will think the car is at WOT (wide open throttle) when you are actually at idle. (see Fig. E below) You will notice that the fast Idle solenoid plug on the DX harness is different then the MPFI setup, this is what I used the 2 pin Molex plug for.

Step 4: wiring the ECU

Before we begin... you have two options for completing the wiring at the ECU. Cut and splice, or remove and re-install the pins. Cutting and splicing is easier, although not as pretty. It's also easy to confuse wiring since you will be connecting wires of a different color. The swapping pins option is harder but makes for a cleaner install. I will tell you that removing the pins on the white plug (plug A) is much easier than on the black plugs.(plugs B and C) Removing and reinstalling pins on the black plugs was a pain in the a$$.....You make your decision based on your abilities

Using the pin out charts below, wire the ECU as such......

A. move pin C1 to pin B10 (orange wire)
B. move pin C2 to pin B12 (white wire)

C. attach the Blue/green wire from the distributor to pin C1
D. attach the Blue/yellow wire from the distributor to pin C2

E. attach the Brown injector harness wire to pin A1 (cyl 1)
F. attach the Red injector harness wire to pin A3 (cyl 2)
G. attach the Lt. Blue injector harness wire to pin A5 (cyl 3)
H. attach the Yellow injector harness wire to pin A7 (cyl 4)

Don't forget to ground the shield on the wire for the distributor. on mine I think I grounded it to the Brown/black wire at A16 (wherever the factory shielded wire was grounded...)

Why did I do this ?
steps A & B move the crank angle sensor to it's proper spot for the Si ECU.
steps C & D add the Cylinder sensor
steps E~H wire the injector drivers from the ECU

Step 5: Install the manifold

Installing the manifold is straight forward... put on the gasket, torque the bolts in proper sequence.. blah blah....once again, here I assume you know how to do the basics...Here are a few tips specific to the Si manifold....

* don't forget to install the new coolant bypass hose (the one that looks like a question mark...)
* don't forget about the PCV hose under the manifold...it's a pain to get to but needs to be hooked up
* If you're still using the DX throttle cable you will need to loop it in the opposite direction to work properly
* The vacuum lines have little numbers on them and hook up as such... (as per my Mitchell guide..)
#12: this goes from the Purge solenoid to the small port next to the EACV on the back of the manifold
#21: this goes from the MAP sensor to the small port on the top front of the throttle body
The red/braided hose from the charcoal canister goes to the larger port on the top front of the throttle body.
There are two vacuum ports on the dashpot of the throttle body (at least there was on mine...) on the one pointing towards the drivers side I attached it to a port on the manifold, the other one I just capped... so far so good.

Step 6: pre-check....

Go over all of the hoses, lines, wires, bolts once again to make sure you didn't miss anything. Did you put the coolant back in? Fuel line hooked up ? are there any possible vacuum leaks ?
Once you've determined all is good, plug in the ECU and turn the Ignition on (don't start just yet....) lean over to the passenger side and see if you're ECU is throwing any codes... if not, turn key and cross fingers. If the ECU is giving you a code, consult your manual for what to do and go from there...

In my experience the car started after a few seconds (takes a while for the fuel to reach the injectors...) I needed to adjust the Idle and reset the ECU a couple of times but so far so good (to reset ECU remove ECU and Hazard fuse for 10 seconds and re-install. some books say remove the ECU fuse... some say Hazard... I remove both to be sure)

The finished project.... the DX air intake still fit....
 
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