Obd 1.5 be damned

[Bridgetown]

Looking for info from anyone running a 3400(aluminum Head) engine on a 3.1(small port) ecm. Looking into switching from my current 3.4 (iron head) ecm that runs the engine now. I have heard that the 3.4/3.1 ecms are interchangeable, and the 3.1 ecm would run the 3400 better. True? Anyone actually have an example?

[Superdave]

there are a couple hundred 3400 swapped Cavaliers running around, I'm personally running a '04 3500 on the 1991 computer.


OBD1 computers are just as tuneable as OBD2.. switching either way from OBD1.5 is a good option.

[Bridgetown]

What is involved in switching from the 3.4 ecm to the 3.1 ecm? Any wiring needed, or is it a direct replacement?

[Superdave]

you'd have to either drop in a new wiring harness, one from a Cavalier/Beretta would work or...hack up your current one (that would really suck).

the ECM connectors are different.

[montess408]

what car do you have ? was you car a 3.1L (gen2) motor or was it a 3100 small port motor ? because as far as i know all gen 2 motors where obd1 and then i am not sure on the small port 3100 but i dont think that there is much difference from the big port 3100 to a 3400 so it should work good
right now i am running a 3400 on a stock 2.8 obd1 ecu and it's runnin good !

[Bridgetown]

My car is an '86 Fiero 2.8 v6. I still have the original ecm and haness from it that is unaltered.

[IsaacHayes]

I thought the 3100 94-95 ECM had same pinouts as the 3.4L 94-95 RWD ECM?

But if you have a Fiero, you can swap to the 7730 or whatever it is that runs DIS and is OBD1 and tuneable. Just a few pin changes. there is a write up on fiero.nl I believe. There are lots of 3400 tuned OBD1 cars out there. That would be the easiest/best route.