Hmm. I did the switch and I've got a surging idle and a check engine light. The surging idle got a little better after 10 minutes but didn't completely go away. The computer is throwing a code 66 (MAF voltage low), even though the MAF meter is new. I'm not sure what to do here. I did notice that the mesh screen on the MAF was dented when I opened the box.
For now I switched it back to the T-Bird computer. I'm glad I made the changes so easy to reverse!
I decided to do all the wiring myself, and just finished it this morning. Tip: once the wiring is done, start the car and check your power and ground wires at the mass air meter connector. I discovered a bad ground this way.
Now I only have to wait for the mass air meter to show up, then I can make the switch. Fingers crossed...
I couldn't resist a look. The 87 does indeed have a BR/W wire connected to pin 30. So that's something I don't have to worry about. And I took the opportunity to plug in the "Mustang only" harness. So the easiest part is done.
When I look at the ignition switch terminals in the '87 EVTM, it shows a circuit 376 connected to the start terminal, but the wire color is listed as Y/R instead of BR/W. So maybe it's wired with a Y/R wire instead? I'll have a look tomorrow.
I'm glad you posted those '88 diagrams. I almost connected to the wrong end of the neutral safety switch. I've updated my Excel spreadsheet accordingly.
I've devised a way to make it easy to switch back and forth between the computers in case it doesn't work out. It involves two eight-pin connectors that go to the computer and one that goes to the rest of the car. Basically you choose either the "Mustang ONLY" eight-pin connector or the "T-Bird ONLY" eight-pin connector. Those two connectors are on the EEC side and the connector at the bottom is connected to the rest of the car. This scheme requires cutting the TAB and TAD solenoid wires and splicing the "T-Bird ONLY" and "T-Bird or Mustang" connectors in between, but it means that no wires have to be moved on the EEC connector: only added.
They are, but it's nigh impossible to get the box out. It's really wedged in there. You can't just slide it down and out because the car's frame is in the way. Nonetheless, I'll take a second look at it. I'd hate to have to remove the entire blower motor box just to remove the processor.
I went to a speed shop this morning to investigate the possibility of having an expert make the switch. I got the impression that they could do it but they didn't really want to. It was an interesting conversation, though. One question they raised was whether I had repinned or otherwise changed the injector wiring to match the Mustang firing order. I don't think this was done, which raises some interesting issues with using my stock T-Bird computer.
I've made a harness that will simplify the wiring for the MAF conversion, but I have a simple question: how on earth do you get the computer out of there? Is there a way to do it without pulling the dash?
EDIT: I did some Googling and I found a video that shows pulling the blower motor box to get to it.
For what it's worth, here is a link to the spreadsheet I built based on the 1987 and 1989 EVTM's:
Thanks. I went through both EVTM's and built an Excel spreadsheet with the differences in EEC pin allocations. It looks like I'll also have to connect pin 30 to the neutral safety switch. It looks like there's a spot near the fuse panel where I can tap it. I'd attach the spreadsheet here if I knew how.
Yup, I've been over that section. I got my 1989 Mustang EVTM today and it confirms that computer pins 3 and 6 go to the speed sensor and pin 19 goes to the fuel pump relay. Pin 6 is really just a ground though and can be grounded right at the computer. I can connect pin 3 to a wire coming off the speed control module. That only leaves the fuel pump relay; I have no idea where that is. The T-Bird EVTM says its above the right rear wheel well -- I guess I take out the back seat to get to it? I've never seen that relay.
I ordered a 1989 Mustang A9P and EVTM book so I can see what has to be done for a MAF swap. Hopefully comparing the Mustang EVTM with my T-Bird one will show all of the differences. I already have the Mustang split tube, but no mass air meter or barometric pressure sensor yet, but I'll get all my ducks in a row before attempting anything.
That's exactly what I'm running, the T-Bird SO EEC, as I started with an SO 5.0 and upgraded it to HO specs. I had my mechanic friend try a mass-air conversion but he couldn't make it work; he said it ran better with the stock computer. I don't know if the pinout differences tripped him up or if it was something else. I wonder if I need to go to a speed shop. I think I need an expert, and I'm not it.
Question: will an A9L work for an auto trans? The one I'm seeing on ebay says it's for a manual trans.
EDIT: I found the answer. Looks like I need an A9P since I have an AOD.
Thanks. The reason for these questions is because I've had the changes in my sig yet my engine sometimes runs very rich. I wonder if it's either from bad O2 sensors or because I'm still using my stock computer. I just double-checked my firing order for kicks and it's got the HO firing order, and with a Mustang GT cam it should be getting plenty of air. Has me scratching my head.
