How can I tell if the computer is bad?

[68converted]

I did the 5.0L conversion into my 68 with the AOD. I had to shelve the project for a few years due to two separate family illnesses. Now broke and needing to move the stang, I am trying to get it started with no luck.

Symptoms: Cranks and starts, but will die after about 10-15 seconds unless feathering the throttle. When doing this, it also pops thru the intake I think, and the exhaust smells of gas. I have tried to adjust the timing per instructions from JRinker's posts. So now I am looking at other issues. Because the SOB that sold me the engine screwed me in the beginning, I am working with what I can only surmise to be an 89 Lincoln harness, so most of the wire colors or locations were all messed up. There is a test port, with the single wire gray plug but again the wire colors are all off and the locations in the plug are diff too. Nightmare to say the least.

To be perfectly honest, I have no idea what I did to get it running in the first place. LOL It has been too long and my notes are missing. So I figure I will test the computer first and work back to the engine sensors.

One note is that I do not have any of the smog components, and TAB/TAD, and a few other sensors are just hanging unplugged. I do have the EGR, TPS, Air bypass, Baro, Exh. O2 sensors, ACT in #5 runner of Explorer intake, all connected. How do I tell if those sensors I have connected are good?

Question is, do I need to have some kind of resistors or dead end plugs for the sensors not connected? Will these cause problems with drivability if not used? I have no way of putting the smog stuff back on as it all went to the recycling company years ago.

Thanks for the help if you can.

 

[68converted]

P.S. If anyone wants to donate an 89-91 harness to my cause, I would be oh so thankful.

 

[jrichker]

Start by dumping the codes...

Dumping the computer diagnostic codes on 86-95 Mustangs

Revised 19-May-2009 to update drawing for dumping the codes on 86-88 Mustangs with no check engine light.

Dump the codes and see what the computer says is wrong…Codes may be present in the computer even if the Check Engine light isn’t on.

Here's the way 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. You watch the flashing test lamp or Check Engine Light and count the flashes.

Be sure to turn off the A/C, and put the transmission in neutral when dumping the codes. Fail to do this and you will generate a code 67 and not be able to dump the Engine Running codes.

Dumping the Engine Running codes: The procedure is the same, you start the engine with the test jumper in place. Be sure the A/C is off and the transmission is in neutral. You'll get an 11, then a 4 and the engine will speed up to do the EGR test. After the engine speed decreases back to idle, it will dump the engine running codes.

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. You watch the flashing test lamp or Check Engine Light and count the flashes.

See Troublcodes.net Trouble Codes OBD & OBD2 Trouble Codes and Technical info & Tool Store. By BAT Auto Technical

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.

The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.

89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.

The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.


WARNING!!! There is a single dark brown connector with a black/orange wire. It is the 12 volt power to the under the hood light. Do not jumper it to the computer test connector. If you do, you will damage the computer.

What to expect:
You should get a code 11 (two single flashes in succession). This says that the computer's internal workings are OK, and that the wiring to put the computer into diagnostic mode is good. No code 11 and you have some wiring problems.

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.

Alternate methods:
For those who are intimidated by all the wires & connections, see Actron® for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.

Or for a nicer scanner see Digital Ford Code Reader (3145) – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $30.

 

[68converted]

Sorry for the misspell on your name jrichker. I wish I had the wire colors listed on the test port you have above. None of mine are similar. I fear that if the computer is not bad now, it soon would be if I jumper the wrong wire.

Let me crack open some boxes, to find my splice notes so I can trace some wires in my frankenstien harness tonight and I will get back with you.

Thanks for the reply!

P.S. No test light installed. There is a wire, just need to find where I tied it back under the dash.