92RedRallySprt

Will a ECM out of an '87 IROC work in my '92 RS???? I know the '92 has an electronic speedo....will anything have to be changed???? If so, what?

RBob

iTrader: (1)

It depends. An '87 IROC could be TPI or TBI. The '92 RS could be TBI or a 3.1l MPFI. TBI to TBI the ECMs will swap.

TPI to TPI, only if some re-pinning and sensor swapping is done. If both TPI the '87 is MAF and the '92 is SD. Different animals and not directly swappable ECMs.

Can you give us a better idea of which engine EFI system is on each vehicle?

Thanks,

RBob.

92RedRallySprt

the '87 IROC is a 305 TPI......the '92 RS is a 305 TBI

RBob

iTrader: (1)

If you are staying with the TBI in the '92 then no, won't work. The '165 won't run a TBI engine. If you are switching to the TPI setup in the '92 then yes, it will work.

The '92 TBI already has a separate VSS buffer box. This is currently driving the speedo, cruise and ECM speed inputs. Just move the one wire over to the '87 ECM VSS input.

RBob.

92RedRallySprt

So, the ECM doesn't control the electronic speedo??? If it does would a ECM out of a '92 TPI car work???? so that it would have the electronic speedo...?

RBob

iTrader: (1)

Not on a TBI f-body. The VSS feeds a 4-out buffer box (go here for a pic of box: https://www.thirdgen.org/techbb2/sho...hreadid=213514) and the buffer box drives the speedo, ECM & cruise.

If you use a '92 SD ECM (1227730) then the 4-out buffer box goes away. The VSS will feed the ECM directly with it feeding out to the cruise & speedo. Of course this ECM ('730) can also accept the VSS info from a 4-out buffer box if so desired.

RBob.