Question about switching to a Mustang GT cam

Topic: Question about switching to a Mustang GT cam (Read 3082 times) previous topic - next topic

Re: Question about switching to a Mustang GT cam

Reply #15 – June 19, 2023, 09:24:45 AM

EEC processor is indeed behind the passenger side kick panel. Remove panel, remove insulation. There is a white-colored plastic bracket holding the processor in at an upward angle; one bolt (10mm?) needs removed and the bracket can swing out of the way-ish, allowing the processor to drop down. The wiring harness is held in by one 10mm bolt.

Re: Question about switching to a Mustang GT cam

Reply #16 – June 19, 2023, 02:22:17 PM

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.

Re: Question about switching to a Mustang GT cam

Reply #17 – June 19, 2023, 06:28:55 PM

Don't go back to that shop. They don't know what the F they're talking about.

The injector pulses are controlled by the EEC. The firing order is controlled by the cam, via the distributor.

The EEC is easy enough to get out. I'm not following how the blower motor is seeming to be in the way...?

I guess the easiest, Beau-podunk way to explain is like this LOL: sit in the passenger seat. The little triangular panel to the right of your right foot....you take that out. The EEC is behind it. 2 smallish bolts and a little wiggle and she's free. Sticl the DA1 or A9L in there (assuming you've went ahead with the Mass Air) and installation is the reverse. Except you won't have to sit in the pass. seat again

Blower motor shouldn't be anywhere in the way at all I think..? Been some time since I was into a Tbird but I think a Fox Stang is identical in layout...

Re: Question about switching to a Mustang GT cam

Reply #18 – June 19, 2023, 11:50:52 PM

When the cam changed the firing order it also changed the sequence of the intake valves opening.
Your stock EEC is firing the injectors in the wrong sequence. The injector should fire when the intake valve close to it is open.

If your EEC has a Brown/White wire on pin 30 you're OK there. The 88 EVTM shows it wired. They may have made the change in 87 but the EVTM didn't catch-up untill 88.

Re: Question about switching to a Mustang GT cam

Reply #19 – June 20, 2023, 11:11:06 AM

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.

Re: Question about switching to a Mustang GT cam

Reply #20 – June 20, 2023, 06:36:56 PM

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.

Re: Question about switching to a Mustang GT cam

Reply #21 – June 20, 2023, 08:35:42 PM

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.

Re: Question about switching to a Mustang GT cam

Reply #22 – June 20, 2023, 09:10:39 PM

Good news.
The 87 EVTM shows the circuit connected for the 3.8L and 2.3L engines.

Re: Question about switching to a Mustang GT cam

Reply #23 – June 25, 2023, 09:03:31 AM

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...

Re: Question about switching to a Mustang GT cam

Reply #24 – June 26, 2023, 07:08:34 AM

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!

Re: Question about switching to a Mustang GT cam

Reply #25 – June 27, 2023, 02:09:57 PM

From the 93 Shop Manual, Mustang 5.0L:
With the engine running, you should have between pin 50 and pin 9, 0.36-1.50 volts
You have a SFI engine.

Re: Question about switching to a Mustang GT cam

Reply #26 – July 02, 2023, 12:36:42 PM

Code 66 is a memory code.
Did you pull the engine running codes? You should get a code 26 if the sensor completely broke.

Re: Question about switching to a Mustang GT cam

Reply #27 – July 03, 2023, 02:05:19 PM

According to the manual with the code reader I bought, 66 (continuous memory code) is MAF voltage too low. I didn't pull any engine running codes.

Re: Question about switching to a Mustang GT cam

Reply #28 – July 04, 2023, 03:56:55 PM

Just a question...did you by chance ever replace the IAC or TPS?

If one of those are faulty, you'll have idle issues. I had a TPS out of range on a 94 truck and while it affected idle and throttle response, there wasn't a code.

Also, disco the battery cable for a few and let it sit, maybe tap the brake pedal and cycle the ignition off/on 4 or 5 times.

Start from clean slate, as it were, in regards to stored codes, etc.

Maybe it'll clean up, and run right..

Re: Question about switching to a Mustang GT cam

Reply #29 – July 04, 2023, 05:55:49 PM

Continuous memory codes are generated while you are driving. They are stored in the KAM (Keep Alive Memory). When these are the only codes you get, you have an intermittent problem. As Beau stated, they can be reset by disconnecting the battery.

You should first clean-up any "hard codes" found by KOEO (Key On Engine Off) and KOER (Key On Engine Running) self tests.

Warm up the engine before the self tests.

KOEO:
Runs self test and post fault codes or code 11 for no faults.
Code 10, a Seperator, then posts memory codes.
KOER:
Posts a 4 indicating the ECU is for a 8cyl engine.
Runs self tests and posts fault codes or code 11 for no faults.

Run self tests and post all the codes here.