I just bought a 1991 Civic hatch. It has a 1.5L PGM-FI and 4-speed.

What I know:
The motor has been transplanted from a 1988 or 1989 CRX HF. It idles extremely rich and rough. When the throttle is held open above 4,000 rpm, it bogs badly as tons fuel is dumped into the throttle body, a few seconds later the fuel stream decreases and the engine revs normally. It does this cycle every 8-10 seconds as long as the throttle is held open whether driving or standing.

What I've done:
Replaced the plugs, wires, distributor, O2 sensor, MAP sensor, fuel pressure regulator, air temp sensor, idle control valve, and checked every connection in the harnesses.

The computer running it is the PM9 from the Civic. I also have a PM5-A03 to try, but haven't. Honda says the motor originally had a PM8-A03,H03 of L03. What PCM do I need and how interchangable are they??

Any ideas and help would be great. I'm new to the Honda world, but addicted none the less.

Thanks,
Jeff

 

the pm8 is the one you want. as for interchangeability.. i dont think the pm5 will work any better than the pm9 you have in it.

 

Was the car rewired for mpfi?

 

No it was not rewired for MPFI. It has the original Civic harness. It has Dual-Point FI. All the original harness plugged directly into the new motor's connectors as far as I can tell.

 

Might be something with your secondary injector. On the daul points, you actually only use one injector. the secondary one is used for cold starts. SO if it is still sending fuel, that could be where your extra fuel is coming from. You can try unplugging it and letting it run and see what happens.

 

Thanks for the advice. I'll give it a shot. I'm out of ideas.

Jeff

 

just keep playing around with it and keep searching for help, it will come to you trust me. I finally got my timing and idle issues worked out today after about a week of working on it. And the solution was simple. Just got frustrated and wasn't thinking.

 

If the car was never rewired for mpfi then the only ecu you can use is the pm5. Trying to use an mpfi pm9 will not work.

 

yeah thats what I was going to say also. I think a pm9 if for a first gen integra, which is multi-port. You have to run a pm5.

 

The car is an original DPFI car so the wiring plugged right in to the new DPFI motor. I have yet to find an MP8 computer, but I'm still searching. Honda thinks the computers will swap out fine, but their computer is twice what the car is worth. I'll be off the the pick your part yard tomorrow. Hopefully they have something with a PM8 in it.

Thanks for the help.
Jeff

 

You need a pm5 ecu if you are still using DPFI. A pm8 will not run the car because it is an MPFI ecu. I have a pm5 ecu for sale if you are interested. Pm me if interested.

 

Thank you!
I think you have finally answered my suspicions which are as follows:

The HF long-block was originally a MPFI motor, not a DPFI motor, as it is now installed in my Civic.

Due to the design of the HF motor (i.e. cams, timing, etc.), it will not run well when a 'rich running' DPFI induction system and computer (PM5) are used.

In order to make this thing run correctly again, I need a non-HF long-block and bolt all the DPFI equipment to it; or find the harness, MPFI system, and PM8 to bolt to the motor in my car.

Am I on the right track?

I have no less than (4) PM5's that I have tried to make work with no success as they all seem to flood the motor.

Thanks again. Please offer any other ideas or advice you may have. Sounds like I need a different 1.5 liter motor.

Jeff


Modified by laterdaz at 7:28 PM 3/6/2005

 

Am I on the right track in thinking the HF long block in this 91 Civic will not run correctly on the '91 DPFI system or do I need to keep digging for another problem? I've tried 4 different PM5 PCMs, O2, AIC valve, fuel pressure regulator, plugs, wires, distributor, MAP sensor, Air Charge Temp, praying, satan worship, and even sacrificed a blond virgin still with no luck. It stumbles and idles really rich and floods itself above 4000 rpm. Any ideas are priceless.

Thanks,
Jeff

 

This does'nt make any sense to me. You have an HF motor which is mpfi...ok fine...You have a dpfi harness and ecu. Unless you put the dpfi manifold/injection setup on it it will not run correctly. Or you can wire the harness for mpfi and run a HF ecu. If the motor has the mpfi manifold setup on it right now then how does the harness all plug in? It cant.