quote Originally posted by cartercarbaficionado: thinking about a ecm upgrade for the 88 v6 formula 4 speed since I'm getting a little tired of the stock ecm deciding to randomly gain and lose power with no codes or anything and would let me do the larger intake and some quieter but freely flowing exhaust to go with the suspension mods I've got in the mail (just fixed the front suspension and decided it needed some better parts)

So, I kinda went over this in the other response to Yellow88. Full disclosure, I've never swapped out an ECM before... I mean... I've never installed an aftermarket ECM before. But I have done plenty of wiring harnesses and it's not too bad.

For me personally, I think re-doing the wiring harness and replacing the ECM with a more modern system is NOT bad advice. With everything being new, the Fiero runs quite well. But it was designed during a time when ECMs were really just starting to come into their own. The ECM we use in our cars was the first *real* computer control of a vehicle. The prior standard ECM that came in cars started showing up in 1980 with ESC (Electronic Spark Control) and usually controlled a fuel metered carburetor. Then they had some super-basic TBI-controlled ECM that controlled things like the Cross-Fire injected TransAm / Camaro and Corvette in 81-82, and controlled the TBI unit for trucks and a couple of passenger cars.

The MPFI system we used was first used in late 1983 in cars like the Olds-88 or the Cavalier... and it didn't really change through the entire production of the Fiero through 1988. Just a year later, 1989... they had a much, much newer and better designed system with the 7730. Just looking at how computers advanced from ~1984 to 1989... we went from an 8-bit Bus / processor with the 8088 microprocessor at 4.77 Mhz to a 16-bit bus and 32-bit processor with the 80386 at 33 Mhz. Literally worlds away in terms of performance.

The big thing that always seems to get harped on is that in order for a modern ECM to work well, the car needs to be running well already (meaning it can't have any timing, fuel, or compression issues). But... if the motor already runs "ok," then an upgraded ECM will definitely improve everything.

Anyone who's converted an older MPFI system to a newer ECM, or even upgraded to an SFI-compatible system will tell you the performance and drivability is night and day.


Below is a copy/paste (and slightly modified) version of what I posted to Yellow-88's thread.

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My personal opinion is that probably the "best" solution for reliability and improvement in performance and drivability is to upgrade to a MicroSquirt system. If you want to keep your distributor (like I'm doing), then you'll also want to make use of an MSD 6EFI box. The MSD 6EFI is used to convert the signal from analog to digital (if I remember correctly), and of course... also provides a whole host of other benefits including multiple spark discharge (which itself improves idle and higher RPM performance). Anyway, the MicroSquirt system operates at a much higher baud rate than any of the older GM ECMs, including the 7730 and responds much more quickly to changing conditions. It can also make use of the digital EGR.

If you want to upgrade to the MegaSquirt 3, it allows you to convert from a Multi-Port Fuel Injection system, to a Sequential-Port Fuel Injection system. This has several advantages, including better idle, improved and lowered emissions, lowered fuel consumption, and improved horsepower in the low-to-mid RPMs (it has no effect, good or bad, in the higher RPMs). Note, you don't have to change anything... but you will be replacing the entire engine wiring harness (with a new harness).

This is the link to the MicroSquirt System: https://www.diyautotune.com...foot-wiring-harness/
This is the link to the MSD 6EFI Controller: https://www.summitracing.com/parts/msd-6415

Couple of things... the first is that if your engine does not run well now, then it won't run well with a new ECM. A new ECM doesn't really "fix" problems... so make sure your car runs as good as it can in stock form before attempting to replace the ECM. Assing your car does run appropriately... there are a TON of benefits you can expect by going with the MicroSquirt:

- Improved Idle (disables cold start injector)
- Improved fuel economy
- Improved horsepower everywhere
- Improved (reduced) emissions
- Improved drivability (better throttle response, etc.)

Another nice thing about the Fiero, for what it's worth, is that the gauges (except for the shift light), all totally work independently from the ECM. This means that they get all of their signals directly from specific sensors on the engine that, while they may ALSO feed the ECM (some of them), they are independent and will continue to work regardless of what ECM you put in there.

EDIT: When you're doing all this, consider replacing your factory ignition coil with an aftermarket (higher spark output one). They're cheap... like ~$50 for a higher output one. One of the problems is that in the upper RPMs, the factory coil is unable to produce the necessary spark / charge in order to support necessary combustion in the higher rpms. Like... above 4,500 rpms you start to see a loss in performance. I'll say this, people see improved performance JUST by swapping out the ignition coil... engine continues to pull hard in the upper RPMs. https://www.fierostore.com/.../Detail.aspx?s=51065


EDIT 2: MicroSquirt won't do SFI... you'd have to get the MegaSquirt 3. I'm planning on doing this swap (after I know everything else is working), but I'm going to be using the Fast EZ-EFI 2.0 system.


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If you're going to go with one of the aftermarket ones, like a Fast-EZ or Holley, etc... you're going to want to use the MSD 6EFI system, and you'll want to use this diagram I made:




Bottom line, the Fiero's signal from the ignition control module to the original ECM is analog, and the newer systems want it to be digital. The MSD 6EFI does that for you, while providing a ton of other benefits.


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EDIT: I'll just say that if you have a wiring nightmare, it might be better to just completely start over with your wiring harness. Remove the whole damn thing and either replace it entirely, or rebuild it sensor to sensor.

[This message has been edited by 82-T/A [At Work] (edited 05-21-2024).]