Which ECU to use?

[michaelmiller85]

I have 89 Festiva L that i have just converted to a manual using a 91 engine.

I need to get a new ecu, do i get one for an 89 manual, or for a 91 manual festiva?

Michael

[kzbill]

you will need to post more information to get a good answer.
Did you use the carb and intake?
Or did you try to convert to fuel injection?

[FB71]

89 auto was efi, Bill.

The important question, Michael, is did you use the 91 distributor and engine compartment wiring, or did you use the 89 dizzy and wiring?

if you used the 91 dizzy and wiring, you need a 90-93 ECM

if you used the 89 dizzy and wiring, I don't know what to tell you... 89 4spd and 5spd cars were carbed only. The auto cars were the only ones with efi, and it was a unique to 89 system.

[michaelmiller85]

I used the harness and and ecm from the 89 with the engine and distributor from the 91. The engine is running just fine using the 89 ecm, but it holds the rpm's high for a couple of seconds before letting them drop as normal whenever shifting. I could live with this problem, but it's just really annoying and does a lot more clutch wear.

[FB71]

switch the dizzy over the '89 unit. The 90-93 dizzies need a signal from the ECM to alter timing, which affects engine speed. The 89 ECM doesn't broadcast that signal.

[michaelmiller85]

So, although i'm using a 91 Motor, i need to switch over to the 89 manual ecm. THey didn't have a Fuel Injected 89 with a manual.

WHat is the difference between an ecu and an ecm?

Michael

[FB71]

WHat is the difference between an ecu and an ecm?

^^^ the last letter!

U = Unit, M = Module... same thing

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So, although i'm using a 91 Motor, i need to switch over to the 89 manual ecm. THey didn't have a Fuel Injected 89 with a manual.

no, no, no. use the 89 dizzy with the 89 auto ECM. Try that first, then let us know.

[michaelmiller85]

Just out of curiosit, if i got a 91 ecu and a engine harness for a 90-93 festiva to go with my 91 engine, would that do the trick?

How hard is it to swap out the engine harness for the festiva?

I would try the 89 distributor for the auto, but don't even know where to find one.

Michael

[FB71]

I would try the 89 distributor for the auto, but don't even know where to find one.

wasn't there one on the engine you took out?

and swapping the harness isn't mentally difficult, but it is physically a pain in the butt.

[25Horseplay]

Put a want ad for a dist. in the FS forum.

[michaelmiller85]

do you think a distributor would make that much of a difference?

[FB71]

absolutely! The '89 dizzy used both a mechanical and vacuum mechanism for spark advance. The '91 relies soley on an electronic signal from the ECU, which the '89 ECU does not send. Therefor, your timing is locked, which will cause poor fuel economy, questionable performance, and unusual driveability problems (like a high rpm between shifts).

[michaelmiller85]

Well, i will start looking for one. Assuming that it does work, thanks for the good info.

But worst case scenario, it doesn't work, could i have the 89 auto ecu reprogrammed to fix the problem? What are my options.

I will hopefully order the distributor today.

Michael

[michaelmiller85]

I just found out from my friend that i owned the car from that the distributor is for the 89.