Electrical 1993 LX 5 speed ECU problem?

I still have my slide rule.

@senorpavo I hope you are happy with the solution. The computer used to be the last thing to suspect on the test lists. But with aging capacitors and fools messing up the wiring, I suspect places like CPU fix will be getting business regularly.
I also suspect you will need to be more wire chasing before this is fully solved. Something I found handy is an extra set of multimeter leads. On them, I have extended the wires and have a clip I can put on the end of either lead. Make the longer lead long enough for one wire to go the entire length of the car and even taillight issues are easier to solve.
@Blown88GT Slide Rule? The only slide rule I have is protect my trombone’s slide. So did you buy your 88 Mustang new? I really wanted the blue over silver GT Ford had in so many two page ads for the 87. I think I bought my used 79 5.0 in 88. And by the time the 93 Cobra came out, I could have qualified for the loan, insurance and made the payments. I’m not sure i’d Still want to pay that much for even just a new GT. I’d need @General karthief ’s manual calculator to keep track of the decimal point on just the interest.

Bought new Jan, 1988, about $14k.
Silver on lower was called Titanium Accent. I chose the Cabernet Red over Titanium, but it got sold when I went back. Chose Cabernet Red all over, still original paint.

senorpavo said:

Thanks for the diagrams. It turns out that the MAF circuit had a short in the ECU somewhere. I cut the RTN wire and the car ran better, but super rich.

Finally found a re-manufactured ECU and it solved that issue. Thanks everyone!

Click to expand...

I am having a very similar issue. After loads of testing, i found out the EEC was bad and ordered another one from Fox Mustang Restoration. I plug it in, start the car, and its running VERY rich and popping its ass off. I get a friend to do some testing on the EEC with my custom tune and he's seeing funky stuff from the MAF sensor. We unplug and plug it back in and it starts running fine. I go out the next day to start the car and its running like crap again. I unplug and plug it back in and it starts running fine again.

Troubleshooting i've done:
1. Unplug MAF while running good
- This changed the idle so I thought it may mean the MAF sensor was good
2. Checked voltage at the MAF
- 2.3 volts at MAF 5 wire and .21 volts at RTN wire. This was all at idle

At this point, i dont know if its the MAF sensor going bad or the refurb computer i got is bad. This is an SCT BA2400 MAF. Is there any way to narrow down this issue? The only thing that has ever changed in this whole scenario was a refurb computer prior to it crapping out. I've never changed anything else while the computer was bad.

Time to perform the Surging Idle Check List.
https://www.stangnet.com/mustang-forums/threads/help-me-create-the-surging-idle-checklist.698148/