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85 2.5 ECM transmission question. by skywurz
Started on: 10-14-2020 02:06 PM
Replies: 3 (57 views)
Last post by: skywurz on 10-15-2020 12:10 PM
skywurz
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Report this Post10-14-2020 02:06 PM Click Here to See the Profile for skywurzClick Here to visit skywurz's HomePageSend a Private Message to skywurzEdit/Delete MessageReply w/QuoteDirect Link to This Post
Hi All

I picked up a couple more Fieros over the weekend. One is a really nice complete 85 2.5l Auto. I want to do a manual swap but cant find a good answer to my current question. Do i need to find an 85 manual EPROM?

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fierosound
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Report this Post10-14-2020 05:53 PM Click Here to See the Profile for fierosoundClick Here to visit fierosound's HomePageClick Here to Email fierosoundSend a Private Message to fierosoundEdit/Delete MessageReply w/QuoteDirect Link to This Post
No. Manual transmission doesn't care.
When you do the reverse, it matters because the ECM controls the automatic tranny's lockup torque convertor.

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AsaBergman
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Report this Post10-14-2020 05:55 PM Click Here to See the Profile for AsaBergmanClick Here to Email AsaBergmanSend a Private Message to AsaBergmanEdit/Delete MessageReply w/QuoteDirect Link to This Post
To drive it properly yes, to get the swap done no. The auto ROM compensates for torque converter drag, the manual one obviously does not. My 84 2.5 MANUAL had an auto ecm in it when I got it and it would idle at 3k every time I came to a stop, give me an error code pertaining to VSS, and eventually lower after maybe 30 seconds. Other than difficulty in starting from a stop though it drove perfectly so you can get away with running the auto ROM and getting the manual ROM later.

An unimportant note is the ECM uses the same line for torque converter clutch on the auto and shift light on manual so with the wrong ROM you shift light will light up at strange times when it thinks it's locking the torque converter.

[This message has been edited by AsaBergman (edited 10-14-2020).]

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skywurz
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Report this Post10-15-2020 12:10 PM Click Here to See the Profile for skywurzClick Here to visit skywurz's HomePageSend a Private Message to skywurzEdit/Delete MessageReply w/QuoteDirect Link to This Post
Thanks all... looks like i will be on the hunt for the proper EPROM as i will not pass inspection with high idle.

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