very useful wiring diagram for 1993 mustang.

1479 Views 11 Replies 4 Participants Last post by Cobrajet67, 5 mo ago

the1dude

Discussion Starter · 5 mo ago

Doing some research on 1993 Mustang cobra wiring diagrams and have a question I hope can be answered. The veryuseful.com wiring diagram shows pin 11 on the EEC going to "ign/starting". No other diagram I can find for mustang or truck has this pinout. Is this an error? If it's not, where is it connected to on ign/starting circuit? Thank you in advance.

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Cobrajet67

· #2 · 5 mo ago

Do you have a link to this diagram?
Many/most wiring diagrams that you find online are not actually for the car that they're stated to be for. Unless you pay for it you will have a hard time finding accurate diagrams. This also applies to fuse panel diagrams.

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Cobrajet67

· #4 · 5 mo ago

the1dude said:
http://www.veryuseful.com/mustang/tech/engine/images/91-93_5.0_EEC_Wiring_Diagram.gif

This is the one I was referring to. I'm repinning an ECU and using a 93 computer. Trucks used pin 11 for CANP. Truck diagrams also have no extra pin to coincide for this circuit.

Do you mean that you're repinning an ECM harness connector? Why are you using a 1993 Cobra computer?
Without knowing if that diagram is even accurate for a 1991-93 Mustang 5.0 it'll be impossible to tell anything from it with certainty. Many vehicles came with the 5.0 so if it's like most of the other mislabeled diagrams out there it could be for any number of vehicles. I would assume that the 1993 Cobra used the same wiring harness as the 1993 GT but idk for sure.
Do you have a complete Cobra engine as well?
The Cobra had a better intake, GT40 heads, and cam, along with bigger injectors, MAF, and TB. Unless the truck has these parts too it wouldn't make much or any power difference and in fact might reduce your current power output since the ECM was calibrated for use with these parts. If your truck is an auto then that's another issue since the 1993 Cobra had a manual trans computer.

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Cobrajet67

· #7 · 5 mo ago

the1dude said:
Thanks all. I'm thinking it is just a mistake on that diagram. I was hoping the dude that made the diagram would also respond. He has another diagram for 91-93 that shows sensor, but no input to pin 11. Gonna visit local dealership and see if he can give me a print. I don't believe 93 Cobras are pinned different than other 91 to 93 mustangs either.

So you didn't explain why you're trying to use a 1993 Cobra PCM in a Ford truck.
If the truck already has all the parts that I mentioned then it will likely be an improvement but if not you might very well experience a loss of power or if you're lucky then no notable change at all. If you have an auto trans then you're definitely trying to use the wrong PCM.
As I said you can't trust nearly all the free wiring diagrams available on the internet.
That makes 3 of us that think that the Cobra has the same wiring as the GT.

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Cobrajet67

· #9 · 5 mo ago (Edited)

It sounds like a 1995 Cobra R PCM would have been an ideal choice though it would probably be impossible to find a spare anywhere. However, what's more readily available and better suited to your application would be a 1992-95 F150/F250/350 351W manual trans PCM. The basic architecture of the programming would be much better suited and then you could add a chip to it or a piggyback programmer from there. That would make much more sense and there's plenty of them out there.
Idk if using a 302 PCM for a 351W will be a great choice here. With the different displacement calibration between the two PCMs the 24 lb injectors probably don't get the same dwell. Also, the 351W makes power at generally different RPMs than a 302 does. I won't say the 1993 Cobra PCM won't technically work but it might not be the best choice.

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Cobrajet67

· #12 · 5 mo ago

the1dude said:
Noted. We'll find out. I don't have a tuner for EEC-IV and can't see spending $300-$400 dollars for one for a one-time deal.

Krem12 said:
Just an FYI, unless you use the MAF from a 93 cobra, the tune on the computer won't do you a whole lot of good. Fueling will still be off. Yes it'll be closer than a stock 5.0 computer, but the maf curve is a Massive influence on fueling

You'll need a tune basically no matter what unfortunately.

Agreed with Krem12 about a tune being absolutely necessary in this situation. The stock Cobra computer isn't going to be able to adjust anywhere near as much as it would need to with the factory program that's on it. It's expecting to see a 65mm TB and instead is getting a twin 56mm.
It'd be interesting to see if it idles at all. If it does I'm almost positive that there'll be a very clear dead zone for power off idle until the mid to upper RPMs are reached and even then nothing will be metered anywhere near correctly. Like Krem12 said my suggestion is also to ditch the twin TB if trying to use the 1993 Cobra PCM and just get a 65mm. It's still not ideal but it will probably at least run and idle without a tune, I think.
The other better option imo is to use an F150/250/350 351W manual PCM with the twin TB but you'll need a tune/chip/piggyback programmer anyway since even the 351W computer is expecting to see a twin 50mm and not a twin 56mm.
When mixing and matching induction and fuel parts on a port fuel injected computer controlled engine, a tune is a necessity or else it's going to either barely run or have severe issues trying to climb thru the RPMs with totally incorrect air/fuel, timing, injector pulse, etc issues.

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