C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

89 ECM question

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Old Dec 4, 2007 | 02:59 PM
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Default 89 ECM question

First let me say I do have a similar thread on the Scan & Tune section. I will try just specific questions on this thread. Will a 89 run properly with the complete ECM from a 86 if all is equal between the two cars? Doing this should make the 89 scan as a 86? Only difference is no cold start injector on 89. Right? Any help will be appreciated. Thanks

Joel
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Old Dec 4, 2007 | 07:18 PM
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Originally Posted by joeld
First let me say I do have a similar thread on the Scan & Tune section. I will try just specific questions on this thread. Will a 89 run properly with the complete ECM from a 86 if all is equal between the two cars? Doing this should make the 89 scan as a 86? Only difference is no cold start injector on 89. Right? Any help will be appreciated. Thanks

Joel
ECM is the same...differences are in the Prom.....86 runs on $32 code...most 89's are $6E....main difference is that the cold start was deleted, and programming added to compensate for the cold start......
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Old Dec 4, 2007 | 08:18 PM
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Thank you for your reply. Now I need to find a stock PROM for my 89 amd this should help cold starts. Can I push my luck by asking what is $32 versus $6E? I'm trying to educate myself more on the world of ECM's. Again thanks.

Joel
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Old Dec 5, 2007 | 06:37 AM
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In reality the cold start - deleted or active - isn't really going to be anything that you notice. The cold start injector only functions for a Very short time - between zero and 8 (I think that's right) seconds, depending on coolant temperature. Doesn't really do anything that matters.

I deleted the 9th injector from my '85 with the install of Edelbrock runners. With NO changes to anything else - PROM program included - it fires up and idles the same as it did before, even now in the winter, and we have seen mornings in the single digits already this season.

Bottom line is that if you are having a hard/slow start problem the Cold start injector isn't the reason.
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Old Dec 5, 2007 | 09:06 AM
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Originally Posted by joeld
Thank you for your reply. Now I need to find a stock PROM for my 89 amd this should help cold starts. Can I push my luck by asking what is $32 versus $6E? I'm trying to educate myself more on the world of ECM's. Again thanks.

Joel
They denote the identifier of the programming on the Prom...all this is done in Assembly Language...if you know what that is, then you'll understand why we have programs like Datamaster and TunerProRT to help us....unless you are an Assembly Language guru....as for your cold starts, the 89 chip will indeed help you there, as there is a table in the $6E code that you can adjust to add fuel in the startup sequence...it should mimic the cold start injector in the earlier models. On my 85, I deleted the cold start injector, and adjusted this table by adding a little fuel, and mine usually starts almost as soon as I turn the key...even faster than when I had the cold start injector...

Cheers,
Michael
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Old Dec 5, 2007 | 09:18 AM
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Deletion of the cold start without compensating on a stock engine WILL cause starting problems, especially with old injectors. Some cars will do fine without it.
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Old Dec 5, 2007 | 10:19 AM
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''instant'' start when the engine cranks over is the WORST thing you can do to your car...far better to have oil pressure/flow to the bearings before load is applied by explosions in the cylinders...unplugged my ninth injector years ago while using tPi, current lt1 conversion intake doesn't have a place for it, i have an 89 chip on the shelf and it will stay there...you may experience slight delay in cold start.
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Old Dec 5, 2007 | 10:37 AM
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Good info. This was my line of thinking, as I still do want the car to read 1989 instead of 1986 when a scan tool is used. I've only checked with one GM dealer in my area for a stock replacement, no luck. they say part is discontinued. Any suggestions for replacement?

Thank you

Joel
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Old Dec 6, 2007 | 12:55 AM
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All you need is some "nice " person to burn (load) the correct '89 program onto a chip.

Could also go to a professional like PCMforless and get a chip done with all the desirable extras for same money as stock chip..
Fan on temps lowered , EGR /VATS delete , convertor lockup speed changed etc
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