If anyone is considering this swap, just do it. Don't hesitate.
It took a little over an hour to pin the new connectors and could probably be done more quickly but I was being extremely careful with the mapping. I also gave each terminal a little pinch on each side to make sure they had good contact when I plugged them into the new ECU.
I used the board from Moates so that I could program my own chips. I temporarily added a ZIF socket. I highly recommend this setup.
I started with a factory 454/5-speed tune and it fired up and ran on the first turn of the key.
First thing I noticed was the idle was better. I let it run while I checked things out and as soon as it got warm it went into closed loop and the INT and BLM started counting off. I was shocked at how much more quickly the 7427 reacted and made adjustments. I went for a drive around the neighborhood doing some low speed, light load (this is where I was having major issues previously) and it ran great. I could hold an RPM and the INT/BLM would adjust and stabilize within just a matter of seconds. The 7747 never seemed to ever get the BLM high enough to be happy (this may also have been an ECU issue...more on that later). Driving around the block a few times I was able to get literally hundreds of BLM counts recorded, whereas the 7747 would have had maybe 20-25 for that same time frame.
Ran that through the spreadsheet and updated the tune and went around the block again and it feels so much smoother.
I had other issues that I was trying to work through before I did the swap, but something forced my hand. I was pulling the connectors off of my 7747 and one connector would not come out. I had to pry it. The terminal on the ground wire had actually welded itself to the pin on the ECU. It got hot enough to melt the connector and melt around the pin on the ECU. A side benefit is that the drivability issues that I had been trying to work through are now gone. The extreme lean condition at 1600rpm/low load is gone. I'm wondering now how much of my problem was caused by this "remanufactured" ECU? Anyway, before the new ECU went in I loaded up the 12v and ground circuits with about a 7a load and let it sit for about 30 min and nothing got hot and it all behaved. I had previously found issues in the harness so that may have been when the hot ground happened. But more about all that story later.
tl/dr - just go swap from a 7747 to 7427 now and you will be happier.
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Originally Posted by TriumphR3
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