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  • Upgrading an 85 ECM with  a 98 ECM in an 85 Vette
  • Upgrading an 85 ECM with  a 98 ECM in an 85 Vette
  • Upgrading an 85 ECM with  a 98 ECM in an 85 Vette
  • Upgrading an 85 ECM with  a 98 ECM in an 85 Vette

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  1. #1
    Willycool
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    Default Upgrading an 85 ECM with a 98 ECM in an 85 Vette

    Hello everyone!

    There is my situation.... My brothe-in -law has just purchased a white 85 ...(real good shape...I helped em pick it out) and he wants to replace the 85 ecm with a faster processing 89 ecm...

    I think it can be done, if you replace the 85 ecm, wireing harness with an 89 and add some MAF burnoff relays, remove the 9 injector and bypass the spark control....

    Does anyone have any suggestions that they could offer me to assist me?

    Has anyone ever completed this task?

    If so...please help me with some insight and digrams if possible.


    Thanks in advance

    Willycool

  2. #2
    Gone but not forgotten Mad-Mic's Avatar
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    i wouldn't think an 85 ecm to an 89 ecm would matter cause they are still both OBD1 ecm's maybe someone else will chime on this

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  3. #3
    Upgrading an 85 ECM with  a 98 ECM in an 85 Vette Vettelt193's Avatar
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    The basic rule of thumb on Corvette Computers is the same as any other computer... the newer it is, the faster it is... However, I don't think it is worth the PITA and money to swap it out. If you want the engine to run better, you would gain much more by spending the money on a performance part or two.

  4. #4
    Member -=Jeff=-'s Avatar
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    Here is a website from a guy that did it on an 85 Z28 and swapped the 89 type ECM

    There may be some variations on the connections

    http://www.eecis.udel.edu/~davis/z28/ecm_swap/

    Also attached is a copy of the 85 vette ECM connector pinout (Ihave a larger copy if you want it)
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  5. #5
    Member -=Jeff=-'s Avatar
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    Default Re: Upgrading an 85 ECM with a 98 ECM in an 85 Vette

    Originally posted by Willycool


    I think it can be done, if you replace the 85 ecm, wireing harness with an 89 and add some MAF burnoff relays, remove the 9 injector and bypass the spark control....

    to add along with my above post.

    you can repin your current harness, saving the cost of the new ECM harness.

    MAF Relays with sockets are about $15 each I think.

    Just unplug the 9th injector electrical connector.

    You will still use the park control circuit that is in your car..

    If your 85 is Auto you can run 89 code. If not you will need the 88 code for the 4+3.

    I would say about $75 for a 165 ECm off Ebay or by searching, $30 for relays, $40 for an 89 MEMCAL, and approx $30 for MISC stuff you may need.

    So for Under $200 you should be good to go.

  6. #6
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    I have an 85 and I was just inquiring about doing the same and i have the same 85z28 website . Looks pretty complicated , ok, it scared the hell out of me. I was told to go to a salvage yard and take the computor and the connections out of a donor car . The 85 ECM is veeerrryyyslow . but it only effects retrieving info . it takes a lot more time to getall the info you might want for the fine tuning. There really isnt a performance issue. It still controls the same stuff. The newer ECM lets you retrieve more info quicker and it does tell you more. I'm going to leave well enough alone myself. Not as adventurous in my old age.

  7. #7
    rbyrne
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    Apparently GM accidentally produced a performance chip for the '85 only and it's available over the counter at your local dealer with a GM part # and all. A buddy of mine bought one years ago for $60 CDN which is like 10 bucks US. A good parts man should be able to find it or Gordon Killibrew knows. If you have trouble locating the # I'll try to find it for you. REAL CHEAP performance upgrade.
    Thanks HU*LT5 thanked for this post

  8. #8
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    Since I have quite a few mods I went with the stage 5 prom from tpis.

  9. #9
    Member WhalePirot's Avatar
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    Default I don't think it is worth the PITA and money to swap it out. If you want the engine t

    AMEN!

    A faster computer does not a faster car, make!



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  10. #10
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    Quote Originally Posted by rbyrne View Post
    apparently gm accidentally produced a performance chip for the '85 only and it's available over the counter at your local dealer with a gm part # and all. A buddy of mine bought one years ago for $60 cdn which is like 10 bucks us. A good parts man should be able to find it or gordon killibrew knows. If you have trouble locating the # i'll try to find it for you. Real cheap performance upgrade.
    thanks for info,btw could u post the gm perf. E-prom part # if u have located it? Thanks,ge.

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