Running a 88-89 W car PROM in a 90 T(Lumina) with 3.1 v6

[David Papworth]

All of the open loop operational modes will run 10 percent too lean.
This includes start, cold idle, warm-up, and WOT accelleration.
The engine will most likely run OK (might have some cold stumbling
and lean miss-fire). Full-throttle performance will be less than
it should be. Might be lean enough to cause knocking and retarded
spark.

Closed-loop modes, where the oxy sensor is functional, should compensate
out for the larger displacement by increasing fuel above what the look-up
tables are calling for. This includes warm idle and warm cruise.

Putting the correct PROM in place should help full-throttle performance
and cold driveability. Gas mileage might be better or worse, depending
on whether the lean mixture was working OK for the engine, or whether
it was mis-firing/knocking.

But since the engine spends most of
its time in closed loop, and the ECM should be able to compensate,
the overall effect on part-throttle power and gas mileage should
not be dramatic.


> -----Original Message-----
> From: owner-gmecm at diy-efi.org [mailto:owner-gmecm at diy-efi.org]On Behalf
> Of Lafferty, John
> Sent: Thursday, October 26, 2000 5:40 AM
> To: 'gmecm at diy-efi.org'
> Subject: Running a 88-89 W car PROM in a 90 T(Lumina) with 3.1 v6
>
>
> A question for anyone:
> After purchasing a car with an incorrect PROM(AMAS7004) in the
> ECM(1227727),
> discovered
> by the help of chipsbyal at aol.com, I am wondering what advantages
> I can gain
> by finding the correct PROM.
> The car seems to run just fine with the exception of a slow reading on the
> speedometer.  The AMAS7004 seems to be
> for a 2.8V6.  How will this affect my current 'performance' as opposed to
> installing a 3.1 PROM? I'm not really interested in
> high-performance(since it's just a work car), but I would like to have
> better fuel economy.
>
> Thanks to all...
>
>
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