please help my 87(ecu question)

1slo 5oh

New Member
Mar 18, 2006
hello to everyone. i am new here.
i have an 87 gt with mass air conversion and 5 speed tranny.
:shrug: :shrug: :shrug:
ok this is the problem.
the car had a 94 5.0 5 speed computer is it, it would idle and drive perfectly, except :shrug:this computer would send waay to much fuel to 7 and 8 cylinders and flood themout.....there fore running on 6 cylinders. i swapped injectors ad was the computer
i put an 92 lx 5 speed computer in it and all the cylinders ran fine...but the car will surge some, then idle good, then jump to 3 grand,and eventually die. also, while i am driving it, it will accelerate by its self alot.
i was told that i need to find like an 88 89 mass air ecu to work with the wiring. but i haaave no ecu it idles...but only 6 cylinders......other all 8....just idle and go whenever.

thanks for reading this and possibly helping
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The 95 computer is electrically incompatible with the 93 and eariler wiring harnesses. The electrical contact layout is different. See for the differences.

Dump the codes and see what the computer says is wrong…

Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great.


IF your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

Codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

For those who are intimidated by all the wires & connections, see for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Walmart.

Or for a nicer scanner see – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $35.
1slo 5oh said:
thanks...will do
the car has mass i need an 87 mass air conversion computer?

Use an A9L for 5 speed, years are 89-93. The A9P will work for 5 speed if you can't find an A9L.

You should still dump the codes & post your results. Most of the problems are sensor related, and the computer dump gives you some direction for finding and fixing them.
1slo 5oh said:
i have the a9l ecu in it now though. sine it is an 87 wiring harness, doi need an 87 mass air ecu?
87 year Mustangs never had mass air. You need either a conversion kit or a harness out of an 89-90 Mustang. Since you say that the car already has a Mass air conversion, you would use an A9L, A9P or A9S computer.

Here's a book that will get you started with how the Ford electronic engine control or "computer" works.

Ford Fuel Injection & Electronic Engine Control 1988-1993 by Charles Probst :ISBN 0-8376-0301-3.

It's about $20 from see . Select boo...//
1slo 5oh said:
so there isnt any difference in the wiring harnesses...?
thanks...been help ful
The 86-88 EFI Mustangs were Speed Density with the exception of the Califorina 88 model, which was Mass air. The Speed Density harness does not have the MAF wiring, and has several pins in different locations than the Mass Air harness. See for specific details on the differences.

Some companies sell a Mass Air harness conversion kit that adds the MAF harness wiring and instructs you where to move the pins to make the old Speed Density harness compatible with the new Mass air computer. The result is the orginal Speed Density is now modified to be Mass Air computer compatible. It is effectively the same as a harness from a car that was originally Mass Air.

For more information on Mass air conversions, see

Conversion Harness kits & parts